Cool,
the four digit serial numbers on the front of the frame and on the underside of the barrel should be the same size font. The two digit serial numbers on the underside of the 'Locking Bolt', 'Side Plate' and the flap on the rear of the rear toggle should be the same size font.
The "3" stamp on your barrel and front of the frame has me a bit stumped too. I have seen threes with a flat top and with a rounded top in those locations. Its late in the day for me and I had to go into my artilleries to compare in order to find enough serial numbers with threes to make an absolute correct statement. I may be challenged, but I think that both styles of threes are correct. I am more an expert of the old German style twos. I'll leave the threes to the highly respected (by me) Ron Woods.
I hate to challenge another highly respected (again, by me) John Sabato, but I alway thought that there was a fixture used in applying the four digit serial number to the front of the frame and the underside of the barrel. But the fixture was not always tightened properly before the stamping took place on the assembly line. The numbers should be aligned. But, if they are the proper size and style, then they could be off just a little. (A little nit picking here). Since the barrel was rounded and the frame was flat, I think that its reasonable to assume that maybe two fixtures were used. I always have to remember that the Germans were in the middle of a war that was blowing away a lot of men and that this was an assembly line almost ninety years ago.
While your pictures were good, they were not good enough to judge the bluing, the general condition and some of the serial numbers. There is no substitute for an actual physical inspection. But making a determination on what I have seen from your pictures, I believe your gun to be authentic. One of the first things that I key up on is the 'Locking Bolt'. Yours appears the be nice and flat with the appropriate champhered edges. This tells me that it has not been restrawed or messed with. There also appears the be the appropriate wear on the bluing for a ninety year old gun. The grips appear to be good but I would like to know if there is a matching two digit serial number underneath. I think that I would like to make a formal offer of double your money $150.
I would like to offer more, but since all navy Lugers of the model 1914 version and earlier had wood bottom magazines, your gun is not totally correct.
Again, from the pictures that you have submited, I would consider your gun to be a collector quality Model 1914 navy Luger and you should never, ever consider prettying it up by restoring it in any way.
Congradulations!
Big Norm