It has been assembled, & whilst i am not certain from the photo's, the mounts may well be some that I have had made. I've had several small batches of Whitehead bases made, although the dovetail blocks are not mine. 1918 is a bit late for a sniper variant such as this - the contracts were effected in 1915/16 & the couple of original rifles I've ever come across were dated similarly.
Hope this helps.