looks old, with a cow or ox or horse or something else?

approximately 30 mm tall and 25 mm long, weighs 8.21 g

Is the animal a cow? It looks a little thick to be a horse, but for all I know it may be something completely different...

I have larger images but I cut them down to try to keep them from being overwhelming. Please let me know if I overdid it.

Thanks!


EDITED TO ADD:

I have learned from more knowledgeable than me folks that this is Julian II, aka Julian the Apostate. The critter on the other side is a bull. My coin should be this one from Numiscorner.com, which looks like this one in Numista Roman Empire coin, but the weight is closer to at least one of those Julian II and bull Uncertain Germanic coins. However, their designs seem cruder.

Should I add it to Numista? Thanks!

I am not an expert but after doing a little research, weights and diameters are all over the place for this coin depending on which reference you check. This is the one I found that seems closest to your specifications.

https://www.catawiki.com/l/12403421-roman-empire-julian-ii-the-apostate-copper-maiorina-rv-bull