More info:
OFF LIMITS boards "Early production" (more or less first hundred) are labeled O.P.M. as shown in the picture.
OPM is the name of a company owned by one of the TBM shareholder (the "M" of TBM) and means "Organizzazione Paolo Morisi" (Paolo Morisi Organization)
after this first hundred "OPM" has been omitted.
ANother OFF LIMIT version exists, named "SUPER OFF LIMITS"
Fausto Tabarroni (the "T" of TBM) gave me a SUPER OFF LIMITS MARQUEE but the board is somewhere in the old warehouse. One of the purposes for 2017 is to write down the story of OFF LIMITS and TBM (ZACCARIA project is continuing but very slowing because of the tons of docs and pics to consider)