Call Beretta customer service.
Get a copy of the Gun Digest Asembly/Disassembly instructions for centerfire rifles. The Marlin Mod 36 is included.
Beretta would be a place to start, then want ads, gun shops, gun shows
About $225 used.
The 469 is very similar to the 59, 459, and 669. Gun Digest publishes an excellent series on Firearms Assembly and Disassembly and the Part 1 Automaic Pistols volume includes excellent instructions on disassembly of the model 59 series.
The Gun Digest Book Firearms Assembly and Disassembly Part 5 Shotguns has an illustrated description of the model 97 disassembly.
It was made between 1934-1946. 100,030 made. No serial numbers. Your best bet is to find a copy of The Gun Digest Book of Firearms Assembly/Disassembly: Rimfire Rifles by J.B.Wood
Find a copy of the Gun Digest Asembly/Disassembly book for rimfire rifles the Model 190 may be in there with detailed instructions. If that fails, contact a local gunsmith.
A Sears Moels 300 is a Winchester Model 1400. For a manual, go here: http://www.stevespages.com/page7b.htm For disassembly instructions, get a copy of Gun Digest Assembly/Disassembly for shotguns. Aslo, gunpartscorp.com has an on-line exploded diagram for the model 1400.
Gun shop, gun shows, e-gunparts.com
Why would you want to? Oh well, it's your gun and I hope this helps: http://www.rarewinchesters.com/images/Exploded%20Views/1866-73-dissassembly.shtml
Internet, library, gun shop, gun shows.
First, determine which model Winchester 12 gauge you have. Then go to www.stevespages.com/page7b.htm and download the manual. For a more detailed set of disassembly instructions, go to the Gun Digest bookstore www.krausebooks.com/category/firearms_knives and buy the Gun Digest Assembly/Disassembly book on shotguns.