HH makes a great point.
What else may be determined from the ad, which is reprinted here:
herreshoff 12 1/2 hull # 1281 - $10000 (brunawick me)
90% restored needs sum one to finish all original hardware and hull # plaque on trailer great project for the price tex for more info
From the punctuation, or lack of it, one suspects all the original hardware is there, there is a trailer, and it needs work. Maybe not, maybe that's what it needs and all there was left was the builder's plate. I'd also suggest it's a young person ("sum" for some). Perhaps a great grandson of the original owner.
No further information based on your contact Adam? No further pictures than the mounted plate?