Hi,
I've just "won" a 2-10-2 on the famous auction site and along with a small plastic bag containing some Rapido coupling conversions, there's another bag with two small brass bits in.

Excuse the photo as I've not undone the bag as I don't want to lose them. They're about 4 or 5mm long. I thought maybe they're to shim a pair of drivers to gain extra traction but I really don't know. I have no instructions and a web search gives no answers. Has anyone an idea what they are for?
Thanks in advance, Ted