Leave it be. That barrel has been shortened at some point in its life (IMO).
There is no slot to mount the sight.
Shoot in and enjoy it for what it is, a perfect pocket pistol!!
On my .38 SA, I had no sight, but the slot and pinhole were there.
We polished up a washer of the correct thickness, and my father-in-law cut it down to size.
Looks great and has seen many CAS side matches and a few main stages.
YMMV