One is Simplex T+P company, the other is Arcus-Simplex.
There's an Arcus-simplex-brown that's currently around, and has some equipment for sale on facebook.
If you can figure out when Simplex T+P became Arcus-simplex that should give you a rough idea what the earliest year could be for that one.
https://www.facebook.com/pages/categ...7276730124995/