New Soviet made Bulgarian portable torpedo boats according to a CIA report dated 27 September 1957

An item reported that the Bulgarian navy in May 1957 the Soviet Union was to hand over a new type of portable aluminium torpedo boat known as Torpedni Kateria O.S.A. Transported by other ships could the boats be launched in necessary. The armament would consist of 2 torpedo tubes. The cruising speed was estimated to be 50 miles.

Source

The report was published on www.archive.org, document number CIA-RDP80T00246A037600210001-1