I'd suggest that there was a company called 'Crown Works' in Tokyo & that you are likely correct about the maker's name being on your gun. The fact that the markings are in English & that it says 'Japan' would suggest to me that it was made after the war as well. There was a plethora of small machine shops and even several hundred makers of motorcycles in operation immediately after the war, most of it well sorted and the majority were history & gone by the early to mid 50's. I would point you toward the main library in Tokyo to see if any small business records or names of people who were known gun makers remain & also in the direction of the gun club that serves Tokyo today. I know there is at least one where international skeet is shot, but I do not have its name.
Not much help, I know, but there seems to be a giant hole about a lot of solid Japanese shotgun information. My impression is that even before the war, very few Japanese were bird hunters or had the desire or means to have a quality double shotgun, not that there wasn't at least a handful of makers capable of making them.
I examined a Japanese made 28ga, single shot w/a very well made engraved receiver & nicely executed wide rib & 34" full choke bbl. that was a rather intriguing shotgun 20 or more years ago. I was never able to find anything at all about it, but suspect it had been made for a woman or child from a very well connected family to shoot trap with. That's pure speculation on my part.
I look forward to seeing what the markings are on the bbls., receiver and underside of the forearm, if any, as well as the locks if you plan to remove the stock. It appears to be a very nice gun! It is possible that it better replicates a German box lock than the normally found Miroku. I say that looking at the treatment on the fences and the double action screws visible. A look inside would be useful, but no need to chance buggering the action screws; I would not touch them at all as they appear pristine.
Also, specific to your gun from what's depicted, that it was at some earlier time fitted with sling hardware, quite common for European &/or rough shooting use and that the single trigger [selective?] would again suggest post war mfg.