Looking at the Le Mans entrants in the 1950's, I see several (mostly French) racing teams used the abbreviation "Ets" at the beginning of their team name. Eg:
Ets. Delettrez
Ets. Monopole
Ets. Fiat Dagada
Ets. Savin & Leroy
The use of this abbreviation appears to have died out after 1954 and hasn't been seen since. What did 'Ets' mean?