Here's what I can tell you...
515 is the model number (In the beginning Holmes used the model cost as the model number). I believe they are rated at 4 tons per boom.
E indicated it had the optional Axle Cradle.
The serial number TA83219 breaks down as follows.
T = 515 Traffic King (model and name)
A = January
8 = 1948 (T models were made from 1940 thru 1953)
3219 = unit number (numbers went from 319 to 6378)
If I missed anything Spanky will straighten me out!
Mike B
