What is my phone line made of?

[NathanE]

It is silver colour, and I thought it was aluminium.

The BT Infinity engineer said it definitely wasn't aluminium though as it wasn't brittle enough. And he is right as I sanded it with some sand paper and it is gold/bronze/copper colour underneath the silver.

So what is the "silver" coating on top?

 

[NathanE]

Neat. At first you were joking

Is a tin coating good or bad?

 

[NathanE]

Nice. So I've gone from assuming I would have a copper line, to fearing I had a aluminium one, to having pretty much the best you can get... tinned copper!?