Howdy all. I found the Mossberg sub-forum, don't see a model 51 sub-sub-forum. Just acquired a 51(a) in what I think is very nice condition (along with a Winchester Model 68!). Some minor rust issues, the worst being pitting on the front sight hood, and some small fingernail catching spots around the base of the front sight assembly. This one has both the standard rear sight and the peep sight. I just gave it a good barrel/action cleaning, wasn't very dirty for a 77 (?) year-old plinker. There are a couple things I'm not happy about - the forward takedown screw is buggered from bad screwdrivers, and the aforementioned sight hood. I see repop hood and screws on Numrich.
A question: Are both screws the same? I might order two since the rear screw has a sharp edge from bad screwdrivering.
I have attached a somewhat crummy image - I'll do better after I reassemble the 68 (required a repair to the stock) and finish cleaning the stock on the 51. Am very very pleased with these two - particularly the Mossberg. It's quite heavy compared to my 10/22, and with the killer peep sight should be a lot of fun.
Have a nice day...