Universal main

"Universal (Italy) brakes were around pre-WWII. Not sure if they were making aluminum alloy versions pre-war (I have seen late-30s Bianchi with them, but don't know if the alloy ones were put on the bike by the owner at a later date). There were #51 (alum. side-pull, early-50s), #61 (alum. center-pull, early-60s), #68 (alum. side-pull, mid-late-60s). The #61 was their response to the Mafac Racer center-pull, and the #68 was their answer to the Campagnolo side-pull.
Universal's model designations correspond to the year of introduction. Universal top models were always considered "Pro-quality. "

Here's an approximate time line on early models:

mod.35 - 1935 (side pull)
mod.39 - 1939 (side pull)
mod.50 - 1950 (side pull)
mod.51 - 1951 (side pull)
mod.61 - 1961 (center pull)
mod.68 - 1968 (side pull)

From Chuck Schmidt on the Classic Rendezvous mailing list:

Universal mod 61 center pull... A very popular "pro" bike brake in the 1960s...