Serial Number Decode

[ComancheStarFarms]

Just bought an IH 1026.  While trying to decode the serial number I noticed that it appears that only the last 4 digits are useful?  Can anyone explain why the numbers prior to the U seem to not really indicate much?  I’ve seen 2610130, 2610150, 2610166, 2610167, etc. but only the last four digits are necessary?  Thanks in advance - Jonathan 

[Drysleeves]

Last 4 indicate the year and month of production with the correct breakdown info. Many are stamped S-Y to the right of the numbers with S indicating provision for 540 IPTO and Y for the 12 GPM hydraulic pump.