MLVW Identification No. Explanation

[FrankJames]

Trying to figure out MLVW ID Nos. Examples:

36 CW 12 83 XXXXX;
35 OT 03 83 XXXXX; or
35 OO 06 83 XXXXX.

The first two digits are clearly the model 35 = M35 and 36 = M36
The last 7 digits are clearly the year and serial number.

In between there are what appear to be a 4 digit configuration code of some sort, consisting of 2 letters followed by 2 numbers. It's clear that "C" indicates Crane and "W" indicates Winch.

But what is "O" or "T" represented? Or one that has "OO" or "OT"
And, what are the two numbers indicating?

Does anyone have a full explanation of these numbers?

Thanks !