A few nice precision turned parts China images I found:
Porsche 917K 1971 – silver Martini & Rossi #23
Image by wbaiv
According to the plate welded to the chassis, behind the engine, this is 917-019. That’s a factory number, 001-099 are for cars that Porsche ran themselves, 101- are cars built for an external customer. In in the case of the 917, any number in the range 1-25 would have been in that astonishing batch that were built all at once in 1969 to qualify the design with a >3 litre engine- 4.5 as it happened, but legal up to 5.0 as long as 25 had been built… This was intended by the FIA to allow the older cars from the middle 1960s to continue being used- Ford GTs, Lola T-70s, while new build prototypes were to be restricted to 3 litres. Well and good, and John Wyer’s independent Gulf GT-40 team beat the 3.0 litre Porsche 908s in the 1968 Le Mans.
Whatever the intent of the rules, what they said was engines up to 5.0 litres if 25 or more cars had been built… So the racing department proposed to build 25 cars at the start, qualify the big engine, and use the stock of parts thus produced to support several years of factory and customer racing. An all-hands effort saw every employee available assembling the original 25, and when they were all complete, the FIA was called to certify that there were 25 and the engine size could be up to 5.0 litres… This set the pattern for Porsche and rule books for the wild 1970s, and even through the 1990s GT1 era.
Ferrari *did* eventually do the same math and built 25 of their 512 GTs. Like Porsche they then took the majority back apart and put the pieces back in the bins, after they had been counted.
The 917 had been built but it was hardly developed, and the 908 was the chosen vehicle for the 1969 season. The Gulf-Wyer team won Le Mans again (same chassis), and Porsche took the point and hired Wyer to run their 1970 season and beyond…