He looks more like an anery to me versus a charcoal. But since anery masks charcoal, he might be both.
As for being diffuse, while his belly gives the impression of being without checks, I have seen as well as produced some that have mostly a plain belly but a few checks right along the edges, just like yours shows. Since they did not have the side diffusion, like yours, I labeled them as not being homo diffuse until their new owners could prove otherwise through breeding trials. The mask gene can also produce the head and belly pattern seen in many diffused, and in many cases, both the diffuse and mask gene is present, but not always necessarily so.
Do you see any bleeding of color on his belly? Do you see any "transparent" scales on his belly? Both of those can be seen in homo diffuse snakes. Here is a good example of the color bleeding and "transparent" scales: