The black belt certificates are old. (I have 2 -- from 1986 and 1996 -- shodan and nidan).
I'm 61, and while I plan to live to 90 or so, I'm sure I won't be around forever. I just had the second one framed to match the first one, and wanted to attach good, accurate translations to the backs of each so my family members would know what they were and exactly what they said.
The only thing I wasn't sure about was the certificate number.
In modern Japanese they number some things using the arabic order just with Japanese characters. You see this for page numbers in modern books for example.