Firstly, I think you may have made a wise move by restoring your old spring rather than going for a new one, as a surprising number of people ( including me ) have found new some springs to be very disappointing .I sent one back to a well-known supplier, (who readily refunded me, to be fair)
For a Mk 1V, Ie with swing spring, there would have been eight of these.
There seems to have been two different diameters.
Originals were made of rubber.
Other more suitable materials have been used which are longer -lasting
- including Teflon, polyurethane,Acetal.The most wear resistant is probably UHWPE* - ultra high weight polyethylene.
Different thicknesses of these ‘ buttons’ or ‘insulators’ can influence ride- height significantly ( though this can be usefully exploited if the spring has sagged to some extent)
* I made some from this material, turning them from 41. mm bar stock on a lathe.
It is quite a cheap material but because of its extraordinary ‘ tough / slipperiness’, I found it really frustratingly difficult to work with -producing a growing pile of failures to get eight good ones!
( btw Acetal , perhaps second best to UHWPE but superior to Teflon, is very easy to turn )