I think it‘s from a canon from a ww1 submarine or Torpedoboat. „Ubts u. Tpbts“ stands for „Uboots- und Torpedoboots“ and just means that it was installed on both. But behind it there stand a „K. L/45“ which stands for „Kanone or Kaliber L/45“ (canon or caliber L/45). The „Bordgeschütz: 8,8 cm L/45“ was installed on submarines (Type UCII) and Torpedoboats (Type 1911).I believe this is for a torpedo launcher (hence the UBTS u. TBTS. (unterseeboots und Torpedoboots). Looks like this could be removed as the feet have a Slide (resembles a tounge and groove) This is just my observations. This device would be able to be detached or attached if needed IMHO. Hence the attachment and the Debossed imprint and the inventory number.
Well, that's my two cents.
JustinG