Sorry John,
the rear sight has been installed backwards. I also don't think it is the right site for a Rock-Ola. The dovetail is tapered, that might not be good. I hope it didn't ruin it.
It looks like a type II barrel band, or a type three that has been cut down. I can't quite tell, a pic from the right side by the barrel band spring would help.
I think someone has tried to do a restoration on it.....Frank