There is no hammer and sickle mark. I have never seen Soviet gold or silver lacking that mark.
The "hammer & sickle" mark was not introduced in the USSR until 1958. Before that, from 1927, this "worker's head" mark - there is a hammer at the base of the neck - was used.
It is of more substantial weight than the typical Soviet items also.
This particular stepped rectangular outline of the "worker's head" mark indicated a piece that weighed less than 10 grams; an oval outline was used on items 10 grams and over.
Why would the 7 indicate 1957 rather than 1977 or 1927?
Because the Tallinn Jewelry Manufactory was only operating from 1953-1958. (“Jewelry Manufactory”, I should mention, is a loose translation from my very limited understanding of Russian; I gather it more accurately translates to the equally lackluster “fabricator of fine decorative items”.)
What does the H next to the womans head indicate?
It’s actually the Greek letter Eta and was, from 1946-1957, the mark of the assay office in Tallinn, Estonia. (Estonia and Latvia were independent countries between the world wars, each with their own silver marks; neither became part of the USSR until the 40’s. I mention this because I think from re-reading your initial post that you may have confused the Soviet "worker's head" mark with the similar — but distinct - independent Latvian mark.)
Hoping this clears things up!
Ref: M. M. Postnikova-Loseva, Zolotoe i serebrianoe delo XV-XX vekov: territoriia SSSR, 1995 (3rd ed.)