Your Glenfield model 20 which was made in the year 1978 will bring between 50-100 dollars,depending on overall condition and a good bore.
MARLIN'S WEBSITE! about $13.00 each.
We have virtually all the parts for most Marlin models. sales@countrygunsmith.net
1987
SO much!
The value of a 22 SLLR Sear Roebuck model 42-103.19791 depends on its condition. This gun in excellent condition is valued between 85.00 and 125.00 as of 2014.
SLLR indicates that the weapon is chambered for Short, Long and Long Rifle rimfire ammunition.
Not sure the question are you looking for the model, manufacture date or what? Is it a pump, bolt, or???
Average price for the rifle itself in VG condition is $75-$125. The scope could add some value depending on the type of scope. Worn rifles of course have less value.
Your local dealership is the best place to get a screw for the firing pin on a Sears model 42-103 19791-22cal sllr bolt action gun. Pawn shops often carry them too.
http://www.e-gunparts.com/productschem.asp?chrMasterModel=0840z353&SortBy=DESC
No way to tell based on your description.
The Marlin Mod 25 production started around 1966 and is still sold as the 925. For the exact year of production of your firearm you will have to locate dedicated Marlin collectors. Manuals are available by download from Marlin's website: http://www.marlinfirearms.com/customersupport/manuals.aspx If you want an original, try eBay.