Savage 775a: 16 gauge - seeking knowledge

I was given a Savage 775a 16 gauge by a friend. While I've learned some basics from searching the web, I'm hoping maybe some Savage fans can add to my knowledge. The gun seems to be in pretty good condition (though missing a couple of parts).

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I was able to figure out disassembly by watching videos on Browning's A5 and Remington 11's. None of them really discussed best practices for lubrication of this model. Any advice?

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I was lucky enough to find the friction rings that were missing on eBay - as well as a reproduction owner's guide. the butt plate is not original and doesn't fit proper, so I'm thinking I'll replace it with a recoil pad. Any recommendations?

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I think (but not certain) that these markings indicate that the bore is Modified Choke. Can anyone confirm?

https://static.wixstatic.com/media/2...9bb139~mv2.png

Will any of these numbers help establish the build date, (or tell me anything else about this gun)?

https://static.wixstatic.com/media/2...5b0bd~mv2.jpeg

https://static.wixstatic.com/media/2...f1bf1~mv2.jpeg

https://static.wixstatic.com/media/2...da8b61~mv2.jpg

Killed the heck out of a milk jug today! First shells through this resurrected 775a. Cycled flawlessly with the friction rings I scored on eBay.

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Nice clean old shotgun. Can't really help you with the born on date, but the 29E inside a circle stamp is just an assembly/inspectors stamp. As for the choke, could be modified or improved modified depending on which "system"" it was based on. Only real way to know for certain is to measure the bore diameter mid-barrel and then again at the muzzle. Unfortunately getting a bore micrometer for shotgun barrels is a pricey endeavor ($400-800!). Best to call around and see if there's a reputable gunsmith in your area who has one that could measure it for you. Serious trap/clay shooters will probably be able to recommend a `smith that focuses on shotguns.