I do not believe any Batrite bat with the length indicated on the knob is a pro-model bat. The pro-model lengths, from what I've read, would be found right after the model number, which should be on the barrel brand (it doesn't look like yours has the model number stamped into the barrel). The stamp of the length into the knob would, to me, be an indicator of a store model bat. The stamp of the WEIGHT into the knob is an indicator of a pro-model bat.
The pro-model Batrites that I've handled have all had the "TA" designation; according to the 1930-33 catalogs that I've seen, the "TA" was a higher quality wood that cost more than the "A" bats.
Here's a really good article by Dave Bushing that lays out some specific indicators of Batrite pro-model bats:
http://www.mearsonline.com/index.php...t01returnid=98
-Al