Brown Pneumatic Pistol

I was at a garage sale last summer and saw this air pistol for sale. I Wasn't sure if I should buy it because it had no markings on the gun to identify the manufacturer other then the number 175 on the bottom of the butt. However I could see that it was a beautifully built gun so I bought it. This Christmas my son gave me the Blue Book of Air guns and there it was on page 133, the Standard Model Brown Pneumatic Pistol. WOW ! How lucky can a guy get. I do have some question that maybe someone can answer.
1.The number that is on the bottom of the butt which is 175, is that the serial number ? If so, how many of these gun were built ?
2. They say that this gun came with blueprint instructions Where can I get a copy of these ?

I would like to get an idea of what kind of condition this gun is in so I'm posting some pictures of it in this message to see what you guys think the grading should be.