And here is one with his underbelly. He's currently my daughters 4h showmanship rabbit. They are working on trust here
He looks like a fine castor to me. The ARBA Rex standard calls for a dark chestnut or mahogany brown surface color; some castors look almost black, but they're not quite correct. Steel reduces or eliminates most or all of the agouti markings, especially belly color, and can make the rabbit look darker overall with very small intermediate rings way up at the top of the hair.
Here is a steel Mini Rex , image from
https://wildriverrabbitry.weebly.com/mini-rex-color-guide.html (That's a great resource for rex coat colors, by the way.)
It looks like your buck might be in the beginning or middle of a molt, causing some uneven surface color and a disruption of the ring pattern, but overall I think he has good bands and good intermediate ring color. The Mini Rex standard describes ideal banding pattern as having intermediate rufus ring (A) and slate undercolor (B) of equal width; while the Rex standard does not specify ring width, the M.R. is a good reference, and your buck has the proper ring widths:
My impression is that his black may be faded due to molt, looking almost dark chocolate, though I've never seen an amber (chocolate agouti) with that deep of a chocolate color. Anyway, you can tell he's not a chocolate by his black ear lacing.

When he finishes his molt, the banding pattern will probably tighten up, and his surface color may very well look more black-tipped.
There is quite a range of colors of castor that are acceptable on the judging table, and some judges prefer darker shades while others prefer lighter. Below is a series of castor Mini Rex, all of which were Grand Champions, even the last one which had wideband influence and was really a bit too red to be correct. But color is only 15 points out of 100 in Mini Rex, and even less (10 points) in Rex. So if your buck has lots going for him in terms of type and fur, some variation from ideal castor color shouldn't be a deal-breaker at all.


