Interesting question. I would have sworn the same thing. I just checked through my stash of service books (the small one with the sedan or coupe on the cover, correct?) These are all used ones, in various states of completion, and none of them have the VIN punched. I even have several with the plastic cover and the small metal card used for service work, but no punched numbers.
Not sure if this is what you are typing about. But I did have the "Owner's Service and Warranty Policy" - Passenger Cars - Tourist booklet, it is dated 9/69. Not for a 113, but stamped for a 108. This booklet describers the overall set-up for service and warranty, not the full service plan booklet.
In any case, the VIN is stamped at the top of the booklet and goes through all the pages, four pages, plus front and back covers.