Can anyone tell me the meaning of the number "4" in this St Petersburg 2nd Kokoshnik Mark?

Does the "4" indicate the Assayer?
It is on a bracelet that I believe is by Abraham Beilin. I will upload a pic of the bracelet asap.
The "4" lies on its side nearest the outer end of the clasp tongue,
(it doesn't come out so clearly in the pic, so I added a black "4" to show the configuration).
I have seen a very similar hallmark (on a piece by a different maker) with the number 7, on a post 1908 gold bracelet on a well known Romanov jewelry site, however I haven't been able to find this sort of "keyhole" (my description) mark described anywhere and explaining the meaning of the initial digit.
Thanks in advance for your assistance.