Roger Bleile has forgotten more about engraving than I will ever know and I am not disagreeing with him; but, I would like to make some observations about the engraving. The work on your pistol doesn't look like any known Ogawa engraving that I have ever seen. Perhaps (almost assuredly) Roger has a greater library to reference from and make his decision. Here are a few Ogawa signed pistols I found on the net.
First is a Model 27 sold at RIA with an oak leaf pattern.
Smith & Wesson 27 Revolver 357 mag | Rock Island Auction
Second is a Colt with a floral scroll.
Notice the use of space on both pistols and the matte background.
Hiroo Sugaya was a Japanese master engraver with European training. He also worked at REI alongside Shiro Ogawa. Unfortunately, his work is unsigned but his style of recognizable. I own several engraved Model 60's that are attributed to Sugaya.
Here are a few shots from them.
Again, good layout and use of space, a matte background, and a detailed eagle enlay. Sugaya's style was very much like Ogawa's.
Here is one of the images of your pistol.
As I said in the other thread, I see similarities to the REI work, but I think Sugaya and Ogawa's work is more refined- at least the examples I have access to. That is why I suggested it may have been done by an REI intern. I would like to see the samples that Roger is using as his basis.
Ogawa is said to have signed some but not all of his work. I was unable to find examples of his signature but I would like to see some if anyone has any images.