For five days in August 1957 a Soviet team met Bulgaria across ten boards, every pairing playing each other twice with the colours reversed. The visitors won 11½–8½. Eleven of those twenty games survive here — a partial record, not a scoresheet: three of the ten boards are missing entirely, and nothing in the games list should be read as a table.
The match as OlimpBase records it
OlimpBase's register of Soviet friendly team matches lists the fixture as August 6–10, Bulgaria–Russian SFSR 8½–11½, split 4–6 and 4½–5½ over the two rounds. The register names the visiting side as the Russian SFSR team, not the full Soviet national team, while the game headers call the match Bulgaria–USSR and place it in Sofia. The register doesn't name a host city.
The ten fixed pairings were Neikirch–Taimanov, Kolarov–Nezhmetdinov, Minev–Aronin, Padevsky–Vasiukov, Milev–Ilivitsky, Bobotsov–Shamkovich, Filchev–Krogius, Tsvetkov–Kotkov, and two women's boards, Asenova–Borisenko and Ivanova–Tikhomirova. Bulgaria won only three of the twenty games — Minev over Aronin, Padevsky over Vasiukov, Ivanova over Tikhomirova — but drew eleven of the remaining seventeen, and the draws are what kept the margin to three points.
Bulgaria's board one, Oleg Neikirch, was the reigning national champion: 1957 was the last of his seven Bulgarian titles and the year FIDE made him an International Master. He drew one game with Mark Taimanov and lost the other.
The games
Eleven games are preserved, covering seven of the ten pairings. Both games survive from Neikirch–Taimanov, Kolarov–Nezhmetdinov, Minev–Aronin and Milev–Ilivitsky; one each from Filchev–Krogius, Tsvetkov–Kotkov and Asenova–Borisenko. The Padevsky, Bobotsov and Ivanova boards are absent altogether, so the eleven scores here cannot be added up into the match result — that comes from OlimpBase.
For one of the visitors this small assignment was very nearly the whole of a foreign career. Lev Aronin — eight times a finalist in the Soviet championship, and second-equal behind Paul Keres at Moscow 1950 — never once played an individual tournament outside the Soviet Union. The European Team Championship at Vienna and these two games against Nikolay Minev, both in 1957, were his only trips abroad; the archive holds both of them, and Minev took one.
Result
We have 11 games from this event. The full results are not known, so there is no cross table; the games are listed in their original order.