D.B

[1930]

These are two pages from a preliminary Dodge parts manual, any idea what the letter before the part numbers might mean, this is a 29, I have a 27 and 28 and neither of those have these letters.
In looking for some sort of a pattern I did notice that hardware related items carried a Z before the part # but some of this other stuff does not make as much sense for instance the Q before the socket wrench for disk wheels and another Q before the tire pump. Alot of suspension parts have ED or EB ect
Any ideas