book on it is 70 to 100 built between 1939 and 1965
Blue Book of Gun Values
According to the Blue Book it should retail for $195 in 60% and $440 in 100% original condition. Add about 10% if it has a single trigger.
A breakdown of the parts for a Stevens Savage Arms Model 9478 is found in the book The Gun Digest Book of Firearms Assembly/Disassembly Part V - Shotgun. It has exploded views of the stock and its availability on the market.
Blue Book of Gun Values
The Savage 99 was manufactured from 1899 to 1950. There is a serial number list in the back of the Blue Book of Gun Values. There are over 30 listings for the model 99. You need to get a copy and identify your particular model.
Contact Savage Customer Service through their website, and request an owner's manual. It should include a parts list/ diagram.
I cannot find a "Savage Model 59A" in any reference book - are you certain of the model number? There is a common Savage rifle, the Model 99A, which was chambered for .303, .30-30, or .300 Savage. The caliber markings will be on the barrel. If it is a .22 then it is almost always chambered for .22 Long Rifle. If it is chambered for .22 short, it will be marked as such. If in doubt, take the gun to a local gunsmith for a professional appraisal. The savage arms 59a is a bolt action 410 shotgun. Should have Stevens name on it above savage arms corporation.
I have a book that says serial number 566,000 was the last serial number used in the year 1950 so yours is somewhere between then and 1960.
Look in the Gun Digest Book of Gun Assembly/Dissasembly #3-Rimfire Rifles. Look in the Gun Digest Book of Gun Assembly/Dissasembly #3-Rimfire Rifles.
Are you sure it's a 940 and not 94-C? According to the Blue Book, Model 94's were made from 1926 to 1945. If you really need to know more exactly when it was made, you can get the Stevens historian's address from the Savage Arms website and send him $15.
You may contact Savage Customer Service through their website. Savage owns the Stevens and Springfield brand names. You did not say what information you seek, so we can't help you further.