Blue Book of Gun Values, old gun catlaogs, gun shops, gun shows.
Start at the library.
One who was looking for information on the Classic Army Airsoft rifle would have to go to the NRA to ask them information on it. They know everything you need to know.
One can find more information on the M1A rifle on Wikipedia. There are also videos about this type of rifle on YouTube and one can buy it from the 'Gun Broker' website.
The dealer or person you bought it from would be a good place to start.
Library, internet, book stores.
There are a a number of websites that sell or have information about the rifle "Gilboa". Including but not limited to "slickguns" and their own website, "Gilboa-rifle".
I can find no listing of an ERA rifle in any of my references or on line. Can you provide more information?
Start by posting a question here with ALL markings on the rifle. There IS no information available for some brands.
This rifle must be rare, I can not find any information on it. I did find the following information on these BSA rifles in Mint condition. ( Yes it would be a collectible) Goldstar $450 Superstar $420-$480
Need manufacturer information.
Library, old gun publications, internet.
Blue Book of Gun Values