The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number: 3235-0006
Estimated average burden
hours per response: 23.8
COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
3M CO COM 88579Y101 903 4,739 SH   SOLE   4,739 0 0
ACCENTURE PLC IRELAND SHS CLAS SHS CLASS A G1151C101 724 5,137 SH   SOLE   5,137 0 0
ALPHABET INC CAP STK CL C 02079K107 809 781 SH   SOLE   781 0 0
ALPHABET INC CAP STK CL A 02079K305 2,439 2,334 SH   SOLE   2,334 0 0
AMAZON COM INC COM 023135106 1,687 1,123 SH   SOLE   1,123 0 0
AMERICAN EXPRESS CO COM 025816109 682 7,160 SH   SOLE   7,160 0 0
AMETEK INC NEW COM 031100100 25,219 372,518 SH   SOLE   372,518 0 0
AMGEN INC COM 031162100 223 1,145 SH   SOLE   1,145 0 0
AMPHENOL CORP NEW CL A 032095101 11,231 138,626 SH   SOLE   138,626 0 0
ANGIODYNAMICS INC COM 03475V101 329 16,325 SH   SOLE   16,325 0 0
ANHEUSER BUSCH INBEV SA/NV SPONSORED ADR 03524A108 9,387 142,638 SH   SOLE   142,638 0 0
APPLE INC COM 037833100 5,716 36,235 SH   SOLE   36,235 0 0
ARCH CAP GROUP LTD ORD G0450A105 18,410 688,980 SH   SOLE   688,980 0 0
BANK AMER CORP COM 060505104 1,305 52,959 SH   SOLE   52,959 0 0
BANK NEW YORK MELLON CORP COM 064058100 310 6,587 SH   SOLE   6,587 0 0
BECTON DICKINSON & CO COM 075887109 300 1,333 SH   SOLE   1,333 0 0
BERKSHIRE HATHAWAY CL B NEW 084670702 15,236 74,619 SH   SOLE   74,619 0 0
BLACKROCK INC COM COM 09247X101 1,098 2,796 SH   SOLE   2,796 0 0
BOEING CO COM 097023105 233 722 SH   SOLE   722 0 0
BOOKING HLDGS INC COM 09857L108 11,604 6,737 SH   SOLE   6,737 0 0
BROWN FORMAN CORP CL B 115637209 319 6,705 SH   SOLE   6,705 0 0
CAMBRIDGE BANCORP COM 132152109 874 10,495 SH   SOLE   10,495 0 0
CANADIAN PAC RY LTD COM 13645T100 20,042 112,835 SH   SOLE   112,835 0 0
CASS INFORMATION SYS INC COM 14808P109 1,118 21,135 SH   SOLE   21,135 0 0
CHUBB LIMITED COM H1467J104 456 3,529 SH   SOLE   3,529 0 0
COLGATE PALMOLIVE CO COM 194162103 5,322 89,421 SH   SOLE   89,421 0 0
COMCAST CORP NEW CL A 20030N101 1,316 38,636 SH   SOLE   38,636 0 0
CONOCOPHILLIPS COM 20825C104 516 8,268 SH   SOLE   8,268 0 0
COPART INC COM 217204106 10,290 215,357 SH   SOLE   215,357 0 0
CSW INDUSTRIALS INC COM 126402106 377 7,800 SH   SOLE   7,800 0 0
DBX ETF TR XTRACK MSCI EURP 233051853 237 9,405 SH   SOLE   9,405 0 0
DIAGEO P L C SPON ADR NEW 25243Q205 813 5,732 SH   SOLE   5,732 0 0
DIAMOND HILL INVESTMENT GROUP COM NEW 25264R207 757 5,063 SH   SOLE   5,063 0 0
DORMAN PRODUCTS INC COM 258278100 18,778 208,595 SH   SOLE   208,595 0 0
DOWDUPONT INC COM 26078J100 812 15,186 SH   SOLE   15,186 0 0
DUKE ENERGY CORP NEW COM NEW 26441C204 268 3,102 SH   SOLE   3,102 0 0
EATON CORP PLC SHS G29183103 341 4,964 SH   SOLE   4,964 0 0
ENERGY TRANSFER LP COM UT LTD PTN 29273V100 159 12,060 SH   SOLE   12,060 0 0
ENLINK MIDSTREAM LLC COM UNIT REP LTD 29336T100 112 11,788 SH   SOLE   11,788 0 0
ENSTAR GROUP LIMITED SHS G3075P101 705 4,205 SH   SOLE   4,205 0 0
ENTEGRIS INC COM 29362U104 3,609 129,395 SH   SOLE   129,395 0 0
ENTERPRISE PRODS PARTNERS L P COM 293792107 429 17,450 SH   SOLE   17,450 0 0
EQUITY COMWLTH COM SH BEN INT 294628102 5,493 183,025 SH   SOLE   183,025 0 0
EXXON MOBIL CORP COM 30231G102 353 5,179 SH   SOLE   5,179 0 0
FACEBOOK INC CL A 30303M102 311 2,371 SH   SOLE   2,371 0 0
FEDEX CORP COM 31428X106 294 1,821 SH   SOLE   1,821 0 0
FRP HLDGS INC COM 30292L107 769 16,721 SH   SOLE   16,721 0 0
GRACO INC COM 384109104 8,628 206,160 SH   SOLE   206,160 0 0
HEICO CORP NEW CL A 422806208 42,834 679,901 SH   SOLE   679,901 0 0
HEXCEL CORP NEW COM 428291108 21,840 380,885 SH   SOLE   380,885 0 0
HINGHAM INSTN SVGS MASS COM 433323102 11,495 58,134 SH   SOLE   58,134 0 0
HONEYWELL INTL INC COM 438516106 221 1,670 SH   SOLE   1,670 0 0
HOWARD HUGHES CORP COM 44267D107 947 9,700 SH   SOLE   9,700 0 0
IDEX CORP COM 45167R104 17,591 139,321 SH   SOLE   139,321 0 0
ILLINOIS TOOL WKS INC COM 452308109 872 6,882 SH   SOLE   6,882 0 0
INGREDION INC COM 457187102 13,904 152,125 SH   SOLE   152,125 0 0
INTEL CORP COM 458140100 2,628 56,008 SH   SOLE   56,008 0 0
INTERCONTINENTAL EXCHANGE INC COM 45866F104 19,740 262,048 SH   SOLE   262,048 0 0
INTERNATIONAL BUSINESS MACHS COM 459200101 578 5,081 SH   SOLE   5,081 0 0
INVESCO EXCHANGE TRADED FD TR S&P500 EQL WGT 46137V357 14,425 157,822 SH   SOLE   157,822 0 0
ISHARES GOLD TRUST ISHARES ISHARES 464285105 525 42,700 SH   SOLE   42,700 0 0
ISHARES TR CORE S&P SCP ETF CORE S&P SCP ETF 464287804 1,456 21,009 SH   SOLE   21,009 0 0
ISHARES TR MSCI ACWI ETF MSCI ACWI ETF 464288257 321 5,000 SH   SOLE   5,000 0 0
ISHARES TR RUS 1000 VAL ETF RUS 1000 VAL ETF 464287598 242 2,176 SH   SOLE   2,176 0 0
ISHARES TR RUS MDCP VAL ETF RUS MDCP VAL ETF 464287473 6,854 89,773 SH   SOLE   89,773 0 0
ISHARES TR SELECT DIVID ETF SELECT DIVID ETF 464287168 15,936 178,437 SH   SOLE   178,437 0 0
JOHNSON & JOHNSON COM 478160104 2,487 19,274 SH   SOLE   19,274 0 0
JPMORGAN CHASE & CO COM 46625H100 6,160 63,100 SH   SOLE   63,100 0 0
KAR AUCTION SVCS INC COM 48238T109 18,802 393,998 SH   SOLE   393,998 0 0
LCI INDS COM 50189K103 3,373 50,495 SH   SOLE   50,495 0 0
LEGACY TEX FINL GROUP INC COM 52471Y106 17,179 535,350 SH   SOLE   535,350 0 0
LINDE PLC COM G5494J103 19,753 126,589 SH   SOLE   126,589 0 0
M & T BK CORP COM 55261F104 17,199 120,162 SH   SOLE   120,162 0 0
MARTIN MARIETTA MATLS INC COM 573284106 285 1,658 SH   SOLE   1,658 0 0
MASTERCARD INCORPORATED CL A 57636Q104 12,705 67,345 SH   SOLE   67,345 0 0
MCDONALDS CORP COM 580135101 504 2,838 SH   SOLE   2,838 0 0
MERCK & CO INC COM 58933Y105 1,103 14,439 SH   SOLE   14,439 0 0
MICROSOFT CORP COM 594918104 5,408 53,248 SH   SOLE   53,248 0 0
MOHAWK INDS INC COM 608190104 2,284 19,530 SH   SOLE   19,530 0 0
MONDELEZ INTL INC CL A 609207105 373 9,317 SH   SOLE   9,317 0 0
NEWMARKET CORP COM 651587107 8,621 20,920 SH   SOLE   20,920 0 0
NIKE INC CL B 654106103 333 4,493 SH   SOLE   4,493 0 0
NORTHERN TR CORP COM 665859104 466 5,572 SH   SOLE   5,572 0 0
NOVARTIS A G SPONSORED ADR 66987V109 718 8,367 SH   SOLE   8,367 0 0
NVE CORP COM NEW 629445206 529 6,039 SH   SOLE   6,039 0 0
O REILLY AUTOMOTIVE INC NEW COM 67103H107 14,016 40,706 SH   SOLE   40,706 0 0
ONEOK INC NEW COM 682680103 264 4,886 SH   SOLE   4,886 0 0
PAYPAL HLDGS INC COM 70450Y103 2,367 28,150 SH   SOLE   28,150 0 0
PEPSICO INC COM 713448108 304 2,750 SH   SOLE   2,750 0 0
PERMIAN BASIN RTY TR UNIT BEN INT 714236106 74 12,500 SH   SOLE   12,500 0 0
PETROLEO BRASILEIRO SA PETROBR SP ADR NON VTG 71654V101 1,062 91,657 SH   SOLE   91,657 0 0
PETROLEO BRASILEIRO SA PETROBR SPONSORED ADR 71654V408 367 28,233 SH   SOLE   28,233 0 0
PFIZER INC COM 717081103 671 15,382 SH   SOLE   15,382 0 0
PHILLIPS 66 COM 718546104 207 2,406 SH   SOLE   2,406 0 0
PROCTER AND GAMBLE CO COM 742718109 207 2,255 SH   SOLE   2,255 0 0
RBC BEARINGS INC COM 75524B104 18,021 137,459 SH   SOLE   137,459 0 0
RLI CORP COM 749607107 23,035 333,884 SH   SOLE   333,884 0 0
ROPER TECHNOLOGIES INC COM 776696106 13,822 51,861 SH   SOLE   51,861 0 0
ROYAL DUTCH SHELL PLC SPONS ADR A 780259206 476 8,163 SH   SOLE   8,163 0 0
SCHEIN HENRY INC COM 806407102 10,512 133,881 SH   SOLE   133,881 0 0
SCHWAB STRATEGIC TR INTL EQTY ETF 808524805 1,840 64,900 SH   SOLE   64,900 0 0
SPDR S&P 500 ETF TR TR UNIT 78462F103 8,834 35,347 SH   SOLE   35,347 0 0
STARBUCKS CORP COM 855244109 1,461 22,689 SH   SOLE   22,689 0 0
TD AMERITRADE HLDG CORP COM 87236Y108 632 12,906 SH   SOLE   12,906 0 0
TE CONNECTIVITY LTD REG SHS H84989104 17,149 226,754 SH   SOLE   226,754 0 0
TELEDYNE TECHNOLOGIES INC COM 879360105 16,927 81,745 SH   SOLE   81,745 0 0
TEXAS INSTRS INC COM COM 882508104 2,421 25,618 SH   SOLE   25,618 0 0
TEXAS PAC LD TR SUB CTF PROP I T 882610108 422 780 SH   SOLE   780 0 0
TWITTER INC COM 90184L102 315 10,959 SH   SOLE   10,959 0 0
UNILEVER N V N Y SHS NEW 904784709 457 8,500 SH   SOLE   8,500 0 0
UNILEVER PLC SPON ADR NEW 904767704 456 8,729 SH   SOLE   8,729 0 0
UNITED TECHNOLOGIES CORP COM 913017109 705 6,625 SH   SOLE   6,625 0 0
UNITEDHEALTH GROUP INC COM 91324P102 1,176 4,719 SH   SOLE   4,719 0 0
US BANCORP DEL COM NEW 902973304 299 6,549 SH   SOLE   6,549 0 0
UTAH MED PRODS INC COM 917488108 734 8,839 SH   SOLE   8,839 0 0
VANGUARD INDEX FDS TOTAL STK MKT 922908769 445 3,485 SH   SOLE   3,485 0 0
VANGUARD SCOTTSDALE FDS SHRT TRM CORP BD 92206C409 215 2,762 SH   SOLE   2,762 0 0
VANGUARD TAX MANAGED INTL FD FTSE DEV MKT ETF 921943858 532 14,345 SH   SOLE   14,345 0 0
VANGUARD WHITEHALL FDS INC HIGH DIV YLD 921946406 867 11,115 SH   SOLE   11,115 0 0
VERSUM MATLS INC COM 92532W103 10,348 373,305 SH   SOLE   373,305 0 0
VISA INC COM CL A 92826C839 10,359 78,515 SH   SOLE   78,515 0 0
WATERS CORP COM 941848103 293 1,551 SH   SOLE   1,551 0 0
WELLS FARGO CO NEW COM 949746101 907 19,683 SH   SOLE   19,683 0 0
WHITE MTNS INS GROUP LTD COM G9618E107 7,882 9,190 SH   SOLE   9,190 0 0
WILLIAMS COS INC DEL COM 969457100 248 11,236 SH   SOLE   11,236 0 0
WINMARK CORP COM 974250102 4,159 26,155 SH   SOLE   26,155 0 0
ZIX CORP COM 98974P100 311 54,300 SH   SOLE   54,300 0 0