Hello lads, It's great to hear I am not alone in regards to the confusion in regards to pips. Also nice to hear that I am not the only one who has had trouble trying to match up pips that are missing.
I got these pips quite some time ago in a grouping of insignia. The group was advertized as small box of odds and ends, possibly military. It had a few brass titles, many other pips of various sizes and colours, along with a few collars and cap badges.
I think they could be silver base metal, I never really though about it. I have included a scan of the reverse of one. Also I have included a scan of the slip on they came on.