Gun shops, gun shows, appraisers, Standard Catalog of Firearms.
My understanding is the model 938 was a toy rifle not a bb rifle, but I did find out it was made in 1988
I can find no listing of an ERA rifle in any of my references or on line. Can you provide more information?
I cannot find any reference to a Redfield Rifle...however there are references to Redfield rifle scopes/optics. Does your question relate to rifle scopes?
You will have to contact Weaver to find out.
How old is it? Who Made it? What shape is it in? you need to give more information to find out the value.
Check the on line auctions.
You need to find a qualified appraiser
The W818878 is not recognized. 70B30095 is a number for a Browning Lever action .22 rifle. Use the link to find value
Blue Book of Gun Values
Professional appraisal
You cant, unless you can identify the rifle correctly. Need to know ALL the markings, barrel length, caliber, etc.
You will have to call FN to find out.