Here , I dug through my photo's , as I knew I had one carb number photo which I had noted which car it was from.
This carb is from 1967 911S no. 306615 (I don't have a photo saved of the COA. But I saw it , when I saved these photo's. And the date noted (if they transcribed the correct one) was Nov. 3, 1966. It was a U.S written COA . If you zoom in on the number , it is 40IDS3C1 no. 1491. This car was said to have been very original before restored . I believe when numbers start being posted tied to car serial number . Only carbs from cars which people have a good inkling that the carbs have a good chance of being original to that chassis , should be posted. And I think the carb numbers are going to do a certain amount of jumping high & low , as the motor assemblers were not looking at the numbers. Just grabbing the proper type. That is why also , I believe (?) a 67/68 911S can originally come with a 40IDS3C1 , along side a 40IDS3C (that is after the point when 3C1's were introduced) . But there could be a (general) progression in numbers . It really depends on how many carbs of each type Weber shipped the factory at one time. Remember, I'm believing that EACH type, started with unit no. 1. So there would be a series of numbers starting with No. 1 for 40IDS3C's . Just as there would be for 40IDS3C1's :
I cannot be 100% certain. As I did not make a note, but I believe the motor number of this car was 960841. Maybe someone else saved a copy of the COA when this car was being marketed (or made a note of engine to car / davep ?).