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        Hi there folks, I've been scrolling down the forum archive for answers but haven't found a matching thread yet. so please forgive me if similar questions have indeed been brought up on the forum long ago and already got roasted. 

       Won a cheap bid on a Keuffel Esser Sextant(serial no. 86356, a WWII era Navy-issued piece perhaps?) and received it from mail a while ago. Inspections were made after unboxing and several damages were found: distorted tangent screw thread, lens on the index arm vernier loupe came off(resting on the bottom of the box), oxidized silver arc. Seems that none of the issues are significent enough to render the sextant completely unrepairable, apart from one major problem: missing horizon glass(on a comforting note, the horizon glass retainer/bracket, along with all other essential accessories like telescopes is still present). I was well aware that the horizon mirror had gone missing after examning the listed pictures presented by the seller, still I'm in hopes of finding a spare one inside the box(usual practice among old Sextants）,turned out not to be the case. 

       This Keuffel Esser apparently uses the traditional half-silvered horizon glass design. I've tried and failed to procure a source where such optical unit could be made from a whole glass pane(None were able to silver a glass for just only half the area). I then resorted to having it made into two individual pieces(a glass pane and a mirror with identical dimentions). These two pieces could be assembled into a complete horizon glass if I were to lay both of them on a flat surface and carefully fix them together using epoxy glue, but I'm not so sure if the precision is good enough for daily use when handled this way, even if it does, can it stay that way for extended periods of time? (I fear that the unclipped transparent half might get thrown out of alignment while the glue in the joint circles through contraction and expansion in different seasons, or just fall off in the worst cenarios).

      It has come to my understanding that the transparent half glass somewhat aids in getting a better reflected image,yet a sextant can still function without it, as observed in some german sextants, or in more modern designs, a whole but semi-transparent mirror. So what would be my best option to restore the horizon glass on this sextant?  Should I glue the transparent glass on or ditch the idea completely,omit to fit only the half mirror instead? Or, just getting a semi-transparent one fitted？

     Very looking forward to your ideas.

     Thanks