1. This rule is made of a very white plastic with very black markings. The plastic is rather heavy and has a different feel to other plastic rulers I have come across.
2. On the top edge it has a centimetre scale but on the lower edge it has a 1:25 scale.
3. There are no marking on the back. Whether this was originally the case I don't know but there is no sign of glue or anything to hold paper.
4. The rule is described as "System Darmstadt". This might have been an attempt to appeal to the German market (Czechoslovakia shared a common border with Germany). On the other hand this particular rule was purchased in a flea-market in Kiev, Ukraine.