This IS supposed to be a 1-1/2 frame. The stock books for that time period had "1/2" hand written in as an abbreviation for 1-1/2. They eventually went to a Rubber hand stamp for "1-1/2".
I cover this extensively in my First written work on James Hayes prototype guns. in 2013. in both the DGJ and PP.
The Parker Story incorrectly speculates that the prototype gun that I wrote about was a 1/2 frame gun and that is because of these notations in the stock books. It is a notion that is easily dismissed when looking at the actual gun and also all of the other surrounding entries in the stock books.
It is interesting to see an "OG" research letter. Issued by Remington. I knew that they would do these on request.
Figure 6 - 226709 Stock Book.jpg
See here a scan from 1928 for 226709 and the 3 guns before it. Note the 1/2 frame size notation before the serial. That gun IS a 1-1/2 frame gun.
This is the barrel lug.
101_0863.jpg