WW1? US Military? Artillery? Spotting? Scope. W.G. Pye & Co Cambridge

WW1? US Military? Artillery? Spotting? Scope. W.G. Pye & Co Cambridge US No. 175. Interesting piece. This one has been in my collection for some time, and I have not been able to find any information about this scope. There is some information about WG Pye, and they were in business in Cambridge England during WW1 making optics (among other things) and did supply products to the US Military under contract during WW1. This piece certainly seems consistent with WW1 military equipment, constructed of a brass tube with that black varnish you see applied to everything at that time. The scope is unusual in several ways; on top of the scope there is a rear v-notch and barlycorn front. At the 9 o'clock there is a rear peep to a square front aperture. The reticle (captured as best I could with the camera and shown in the photos) is a grid and quite unusual, with three vertical and two horizontal lines (though two vertical lines are slightly bent).  From scratches on the tube, it appears that there were rings used during mounting (at some point), but it also has a stud projecting as seen on artillery spotting scopes. The glass on the tube is in good condition, but glass is dirty internally (no surprise there) and my eye can't focus on a clear picture when looking through the magnification. I really do not know what this was used for, and it really needs to move on to a new home rather than continuing to languish in a box in my collection. Any information on this piece would be welcome. A fellow collector suggested it might be part of a survey transit, but I don't think that is correct: this is defiantly military and complex in construction. I do not believe a British company would manufacture a product and mark it "US" unless it was for the US Government. Perhaps it was part of an Artillery Forward Observer's equipment used to estimate and adjust fire? This would be closer to a possibility as far as I see it. My belief/theory is that this is a spotting scope for a field gun, but, as I said, I can't find any information. The scope measures 6.5" long, and the scope tube is 1". Please see my store for other items. Please ask any questions prior to bidding. I accept returns for any reason, including buyer remorse and Item Does Not Fit. Please see my other items for sale. I combine shipping if you win multiple items. Payment is due no later than three days after the auction ends or you choose "Buy It Now". Seller internal inventory location: Shelf 3 Tier 2 Box#: SG1