OEM self-limiting rotor buttons, pros and cons

So I will dig up my box of “ignition parts”, someone has moved then about, but I believe I may have a number of NOS “self-limiting” rotor buttons , as pictured below

They are ex-dealer stock, they may be NLA these days ?

I ran the same one for 20 years in my 420G never gave me any trouble

New rotor buttons are of unknown quality , with inferior plastic, metal and rivets

I cannot recall if peoples opinion on them is that these are very high quality, or gave some problem with cutting out ?

I suspect they would not have degraded much over the years despite being NOS ?

fit MKX/420G/E-type/XJ6

all info welcome