M43/M47 shoulderboard buttons

[Slobo]

Some questions for the boards on rimmed (as typically seen with chinstraps and tunic buttons) vs. domed shoulder board buttons for the late war and postwar (to 1958) Red Army and NKVD/MVD, etc. officer tunics. Contemporary collection items (though you never know without close inspection if the buttons have been replaced) and period photos seem to sjggest both styles side by side in the late war years.

- Did one style of button precede the other in production?
- If so, round about which years did each enter service?
- When did each tend to leave service?
- For M1947 MVD/ security service era until 1958, was one style more prevalent than the other?

Hoping to get a better handle on this admittedly arcane issue for dating purposes and simple curiosity.