This is a 917K oil-thermostat which I acquired from ANDIAL. Thank you Dieter! BTW, please spare Dieter the calls, he doesn't have anymore, came off his engine dyno. Here is one recommended method of taking these thermostats apart without damaging the top. We used a precise machinist vise and a couple of custom made aluminum port caps https://pbase.com/9146gt/image/73559587 see here also https://pbase.com/9146gt/image/73559588