This section is still in progress....maybe forever, but see what I have so far while your here. The tile to the left has "canting", the edges of both the top and the bottom prisms are short having a "clipped off" look. Possibly to leave room for a large solder joint in the corners? Not all makers did this. (The corner of the tile to the left of the LIX is the "cant" in case your still not following me.) L IX is a good example of the many different patterns of markings. Letters and/or symbols, Roman numerals, some similar to hash marks. Maker names sometimes as well. Most are on the prism side, some easy to see, some very faint.