The magnetic ones were used by both Modern and ADT I still have a couple of leather fobs somewhere.
The smaller elmdene ones were the replacement and had a set led in the ring which were never used because of the regs but seemed light years ahead of the mag ones. Both had a really positive action, the mag with a clunk as it drew the ball bearing up and the other had a really nice quality 'click' to it.
I only fitted maybe 1/2 dozen ARN1E ones and tbf I think they were over engineered for the application, ADT obviously thought they were overpriced. From memory they were 3-4 times the cost of the others.
If I can find the fob I'll post it out to you, neither are new sadly though.