Right, I was clear on that. At least in my mind. Maybe my post was not clear.

The 400 I have is a Mitsui/SKB 400, the later boxlock with sideplates is an SKB 400 not an Ithaca/SKB. But it has been shown that there was also an Ithaca/SKB 400 based upon the catalogue shown in Researcher's post.

If one were to compare my Mitsui/SKB 400 alongside the Ithaca/SKB 400 I'd bet they were the same gun except for the roll stamping on the barrel and possibly the cosmetics of the engraving.