Anyone know this old AC spark plug designation

My 1954 Cadillac manual calls for using an AC Delco spark plug 46-5. They do exist as I saw one on Ebay. Anybody know what the 5 designates. Later designations were 46 with no letters and 46 S. 4 is 14mm, 6 is heat range, and S I believe is square seat. I don't know what 5 would be though. Thanks for any input. Jim

 

I bet the "5" is a misprint and it should be 46 S.

 

S it is. 45S for my cads.

 

I know that the newer version of AC plugs are 45S but the older correct AC Delco spark plug for a 1954 Cadillac is 46-5.

Here is one someone is selling on ebay right now:

http://www.ebay.com/itm/vintage-AC-...t=Vintage_Car_Truck_Parts_Accessories&vxp=mtr

 

I bet this would help...

http://www.ebay.com/itm/370622496855?