Hey Guys, I'll get you a close up of the Petri horn push on my car tomorrow. It's known as the "ZODIAC" and was manufactured back in the mid 50s. Finding an original one can be very difficult. BFY Obsolete in Orange, Ca has used one 4-sale at $800. Mine was NOS when I purchased it in '96 at a substantial cost. But there is good news for you (bad for me) as Takashi Kimori of Flat-4 has started reproducing them (as well as the Cameo Medallion/Golden Lady & the Rising Sun/Moon) for less than $90
The repro's are great, except the Rising Sun/Moon version. The original 80mm version is supposed to be Red, NOT Blue. The Blue colored version was used on the smaller 65mm-sized horn buttons for VW cars (see pic below). Otherwise, all 3 buttons look great.