It looks like the braze on looks a bit too far back from the head tube to be a race number tag holder.
As also mentioned already, the race number tag holders were usually just present on top of the line race bikes and not on mid or lower level models. But, who knows, maybe they added it on to the frame as a feature for entry level racers to go for.
Maybe a period catalogue from the manufacturer can better confirm what that braze on was really for.
I do see a slight fork "bendage" on that bike in the pic. Hopefully it's just the fork and not the frame that's bent as it should be easy enough to repair that fork.