Spanky,
The Holmes serial number info is:
Cat no. 515E
Serial no. TF7
Model no. 2335
Not sure if 2335 is the model number or the production number.
This GMC wrecker has a chassis ID of EC303, which makes it a 300 Series made in 1946 (from
http://www.oldgmctrucks.com/page0016.html ).