My Speedster has, supposedly, 911 wheels but this Newbie could use some help finding the right spare. Included some pictures but so far my basic research has failed me.
Original Post
I spoke to my Porsche enthusiast/expert friend and he says those do not appear to be authentic/original Porsche 911 rims. He said Porsche 911 never had a four lug pattern. I also checked a website that specializes in Porsche rims and when I selected all years of 911 none of them had a four lug pattern. All of them were five lug. The 914 had a four lug pattern and it was a 4x130. Porsche 924 also had a four lug pattern in 4x108. I'm going to say those are not 911 rims.
Here is a website that will explain how to measure bolt pattern. Once you determine the bolt pattern you can search for an appropriate sized rim to make a spare with.