Hi, Qrt.S.
1. Such order (set) of marking: the sign of the certificate + test mark (a head in a circle + figures of the cleanness of silver in a square only) is described in Rules of a marking-off 1908 («Правила ÐºÐ»ÐµÐ¹Ð¼ÐµÐ½Ð¸Ñ Ð·Ð¾Ð»Ð¾Ñ‚Ñ‹Ñ… и ÑеребрÑных изделий 1908 года). Such order of marking is applied for marking of a silver frame (оправа) of a glass or crystal product. Special for it only.
Mark "main kokoshnik mark" isn't applied. The additional (second) sign (a head in a circle) was put, if there were minor parts.
2. You are right, the right looking kokoshnik was used to May 1927, but Khlebnikov firm was closed in 1917. Therefore I have written the period 1908-1917.
3. The court supplier mark( Khlebnikov) is strongly damaged at finishing processing.
But you are absolutely right: here good photos are necessary. )))
Best Reg..