If you are interested in 99's, then you should buy Douglas P. Murray's book The Ninety-Nine A History of the Savage Model 99 Rifle. It is the best source of 99 info out there, and there are a LOT of irregularities and things that don't match like they should. Like your folding rear site...it doesn't belong on a rifle made in 1936.
But if you like how they look and how solid they lock up and how well balanced they are, look around and find some more. Their value has really jumped in the last 4-5 years.
I am not an expert by any means. But I look at the SN of every 99 I see and memorize all the features and then look it up when I get home to figure what model I was looking at. I picked up an EG with a Lyman peep on it last summer for $300. Well used, but all original. The guy was happy to get $300. I would have paid more.
Brian