Apparently there are three versions of the Russian "pineapple" tube:
Only version I've ever seen is the one on the right, with the three "teats" on the top.
Update 9-20-2015:
The picture above presents 3 tubes, from left to right. First tube is 6C18C production of 1963, 1964 and 1965 (they all look identically). The second tube is 6C18C production of 1968, 1969. The third is 6C33C production of 70s and 80s. Now is a request for a wild guess: even if to presume that the plate materials are the same then which anode would dissipate more power?
Svetlana and Ulyanov 6C18C: