Win 1892 missing serial number

[threebars]

A pard has lent me what appears to be an original Winchester 1892 in .44 WCF.  Curious thing is,  there are no serial numbers in the place where the serial number should be, at the bottom front of the receiver. Instead, that space has been  stamped over with obliterating marks and on top of these marks, "WRACO" has been hand-stamped. I'm guessing that's for "Winchester Repeating Arms Co." Puzzle is, why no serial number? I've checked elsewhere on the rifle, but haven't dismantled it.  Can someone shed some light on this mystery?

Thanks, compadres.
threebars keeton