McCulloch Kart Engine Identification Numbers.                                                                                         Production Period MC-1 ....................................................................................9/61 to 1/62 MC-2 ....................................................................................2/62 to 4/62 MC-5 ....................................................................................2/60 to 6/60 MC-6 ....................................................................................6/60 to 10/61 MC-7 ....................................................................................2/62 to 10/62 MC-8 ....................................................................................2/63 to 11/63 MC-9 ....................................................................................2/64 to 5/65 MC10 ...................................................................................6/59 to 2/61 MC-20 ..................................................................................3/61 to 2/62 MC-30 ..................................................................................2/62 to 10/62 MC-40 ..................................................................................2/62 to 10/63 MC-45 ..................................................................................2/64 to 4/64 MC-45D ...............................................................................4/64 to 6/64 MC-49 ..................................................................................4/66 to 5/68 400160 Serial number Prefix ...13 ............. MC49C           .       6/68 to 6/72 400160 ........................................14........MC49E                   6/72 to 8/76 400162.........................................10 .......MC49 M/C     .        3/73 to 6/75 MC-70 ..................................................................................3/63 to 5/63 MC-75 ..................................................................................1/64 to 3/65 MC-90 ..................................................................................2/66 to 4/66 400165 .........................................10.......MC 91                  12/66 to 4/68 400165..........................................11 ......MC91A                  5/68 to 5/70 400165...........................A12,A13 ... ........MC91B                6/70 to 10/74 400165..........................................12 ......MC91C                5/72 to 10/74 400165..........................................15 ......MC92                  11/74 to 4/76 400165...........................................16 .....MC93                    4/77 to 7/77 MC-100 ...............................................................................2/66 to 3/66 MC-101 ...............................................................................4/67 to 1/69 400167.............................10, 11..............MC91 M/C           3/73 to 10/74 400170.............................10, 11...............MC101                 4/67 to 1/69 400170.............................14 ............ .......MC101A             6/69 to 10/72 400170.............................16 ............ .......MC101AA          2/72 to 10/74 400170.............................17............. .......MC101B             11/74 to 5/77 400170.............................13.....................MC101C               2/69 to 5/69 400170.............................11, 12 ...............MC101D             10/71 to 9/74 400171...................................12 ..............MC101 M/C           4/73 to 6/75

These details taken from the 1979 Publications Guide