I just inherited a ring that has been passed down in my family since WWI. My great grandfather (who was a scoundrel) took a brooch off of a dead German officer in 1915 in Belgium. He had it converted into a ring.
In 1931, my great grandfather coincidentally met the brother of the dead officer. The brother saw the ring and said, "That looks remarkably like a brooch that has been in my family in Bavaria for a long time."
I'm not actually sure if it's a crest, now that I write this. And it's pretty small. If possible, I'd love to figure out how to get it back to that family, but I have no idea where to begin.
https://pro-heraldica.de/en/heraldry/
https://pro-heraldica.de/en/heraldry/terms-of-heraldry/
https://en.wikipedia.org/wiki/German_heraldry
https://heraldica.hypotheses.org/1767
heraldric blazons are their own little DSL, so you'll need to know how to encode the crest into that language. And of course, it's not just one language; it's many that vary by nation-state-ish-thing, time, etc. You'll want to find a herald who knows about the continental blazoning styles.
a database of german arms from ~1600+: https://data.cerl.org/siebmacher/_search/