Help with Navy Luger

[kro]

Have a chance to pick up this Luger at a reasonable price. But would like some help from the experts. I think it is a reworked 1906 altered navy. All numbers match except one grip panel & magazine. The firing pin is unnumbered. It looks like on the back of the grip WK has been X'ed out and I.S.B. stamped. It's not in the best shape as far as finish but the price is right. Any help you can offer about this Luger would be greatly appreciated.