Rear disc M1100

[BRH]

Hi, doe's anyone know, are the 4 pins on the rear disc, that are used for the speedo of my M1100 magnetic or just iron.
Iv got a new wavy disc to fit, but it doesn't have the 4 pickups on it, just 4 holes, so I'm trying to find out what I can do to use this disc and have a working speedo.
Any thoughts ?

Thanks