Patents on safe construction
The Shwayder company seems to be quite famous for the anti-drill hardplates. Shwayder is no safe manufacturer. They develop drill resistant and wear resistant stuff. They have quite a few patents regarding hardplates:
US3049435 filed 1957 (https://patents.google.com/patent/US304 ... =US3049435) coating steel with a layer of carbides.
US3205841 filed 1961 (https://patents.google.com/patent/US320 ... =US3205841) describes a flat steel container ("envelope"), that is filled with carbide pieces brazed together.
US3715999 filed 1971 (https://patents.google.com/patent/US371 ... =US3715999) describes the concept of a hardplate with carbide pieces brazed together and having a rough surface.
US6541124 filed 2001 (https://patents.google.com/patent/US654 ... =US6541124) describes a steel plate which is thinly covered with rough carbide pieces.
On their website is the most important trademark MaxAlloy. They write it is produced since 1951, which predates all Shwayder patents.
There is also a patent by Kennametal, which uses very modern methods. Kennametal is also not a safe manufacturer, but a specialist in carbide drill technology. They filed patent US4608318 in 1981 (https://patents.google.com/patent/US460 ... =US4608318). This stuff is made from fine tungsten carbide grains (or similar) and stainless steel powder. First this mixture it is compressed and then heated for sintering.
I could not find out, what Relsomite, Relsom (read backwards) and Mosler 1061 Rex 49 could be.
Martin Hewitt, Investigator Chronicles of Martin Hewitt