If you are talking about something like the large 63> or <11 painted on tac-signs and sides of vehicles, there was a simple system for the line Battalions.
At that time (late 90's – 2003) each Mech/Armored Divison had 3 Brigades with 3 Battalions per Brigade so total of 9 Battalions.
Starting with the 1st Brigade, the Infantry Battalion having precedence within each Brigade (very important!), Battalions were numbered 1-9.
The exact sequence varied for each Division depending on allotment of Infantry-Armor Battalions within each Brigade, but generally this system was true for 3rd ID, 1st ID, 1st AD.
The Division Cavalry Squadron's were usually a /9x or a 0x, IIRC.
Don't know about the Artillery, Engineers, etc.. but usually those will be the vehicles with / slash too.
The second digit was the Company, the chevron was the platoon. Pointing Up = 1st, Forward = 2nd, Down = 3rd.
3rd ID in 2003 as an example:
<51 = 2nd Platoon, Aco, 1-64AR
1st Brigade: 1x = 2-7IN, 2x = 3-7IN, 3x = 3-69AR
2nd Brigade: 4x = 3-15IN, 5x = 1-64AR, 6x = 4-64AR
3rd Brigade: 7x = 1-15IN, 8x = 1-30IN, 9x = 2-69AR
IIRC 3-7 CAV = /9x
Side note, Ft Stewart units, 3rd ID or 24th ID, didn't use a numbering system before OIF (they just used chevrons with squares), they must have adopted the numbers when staging in Kuwait.
3rd ID was using both systems at the same time during OIF I, so we see chevrons pointing everywhich way. There are a lot of markings the OIF I 3rd ID vehicles that were "non-standard", applied in Kuwait during the build-up for their specific task.
Other stateside units (1st Cav, 4th ID) were using a 4 digit system before OIF, don't know if/when they transitioned to the two digit chevron system.
I always considered this two digit chevron numbering system to be a USAREUR thing, that's were I saw it used the most.
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