1906 american eagle with only 2 digit serial#

[macs guns]

i recently purchased a 1906 american eagle at an estate sale and after i got home i realized it only had a 2 digit serial number on inside frame, every piece has same 2 digits stamped on it, it dosent appear to have reblue, no other numbers appear anywhere on barrel or in front of frame. no apparent grinding or filing, contours compare with other lugers, the chamber indicator is marked loaded not geladin, the dwm on toggle appears to have gold leaf on it, strawing is still visible, everything looks original but no "major" serial numbers. I had the piece looked at, the gentleman said it was a bargain at what i paid, $375, and although he is an authority on lugers, he had no explaination why barrel or frame was not marked with a serial number. any help would be appreciated, any questions about the piece post them in replies and i will return. thanks
mac