I think I can help you with the rear sight. They are aftermarket but might not be from Micro. From checking one of my guns and an original catalog, I am very sure that it was a sight made by John Giles, an old time pistolsmith and the proprietor of Giles .45 Shop that was started in 1951. Because of the appearance, his sights are sometimes called "wagon wheel" sights.
According to the catalog I have, Giles offered stipling on the front and rear straps as an additional option. However, I have never seen a Giles gun without at least the stipling on the front strap.
If there was a flat surface, like a rib, there probably would be an engraving saying "Giles .45 Shop, Odessa, Florida." But here there is no flat surface for doing that, so that is not surprising that the engraving is absent.
Check through your dad's records to see if you can find the work bill, bill of sale and/or a test target. The Giles .45 Shop started in Clearwater, FL in 1951 and moved to Odessa, FL in 1957 and was in business into the 1980s. I remember talking with him over the phone after I acquired one of his guns.
If you can document that John Giles did an accuracy job on this gun, rather than just installing a rear sight, you will really have something. The catalog I have didn't list Ruger .22s, but said that the High Standard .22 pistols he turned out would put 5 shots into 3/4" at 50 yards.
Take it out and shoot it. Best wishes and I hope you enjoy this legacy from your dad.