Keystone Klassic Center caps

According to your measurements & what I remember, those are possibly SHK4 or 5 which fits the 5 on 4" pattern, or 5 on 4/12 & 5 on 4 3/4. The 5 on 5 & 5 on 5 1/2" use bigger caps if my memory serves me correctly. I'm just trying to give information, not other comments.