Those kanji are 黒厚釜 in a handwriting style. This type of structure is fairly common for 厚 in handwriting. You can technically say it derives from 行書, a mildly cursive style. But even if you have not ever heard of it, you would agree that your handwriting eventually looks more or less like this if you have ever tried to write characters rapidly (with the right hand), due to the motor economy.
There does not seem many real examples of 行書 on the internet, but you can try out any 行書 font out there to know its pattern (1, 2):
As for handwritten characters, they are not employed here in order to give some "fancier" impression; in fact, they often symbolizes authority, quality, or of course, tradition. I remember I have mentioned it on another post, in a totally unrelated context:
Let's look at the brand logo of a Japanese whisky. What do you get from the alphabet letters? It gives me impressions of stability, tradition, establishment, authenticity, and a hint of 19th-century flavor... so does the brush kanji. They look so different, but have similar connotations.