The puzzle car is probably the original prototype 4-seat 375L, built by Frua and shown at the Geneva Show in 1968. This was the first 4-seater Monteverdi, and I believe one other similar car was built in 1969; maybe that's the one that Gunter Sachs bought, I don't know.
The 375L pictured in SACO's last picture is, as he says, the production 375L, about 100 of which were built by Fissore and which had a completely different body from Frua's earlier 375L (look at the rear side window).
Wendax's puzzle 1794 is also the Frua prototype, not the Fissore production car, and should therefore be merged. Agreed?