I'm not 100% certain, but I don't think there is a true commercially manufactured 50-50 alloy of copper and tin.
The closest I can think of offhand is Bell Metal. According to Hawley's Chemical Dictionary this is defined as:
"A copper-based hard alloy that contains 15�40% tin and optional additions of zinc, iron, and lead"
Clearly, leaving out the zinc, iron and lead would still give you Bell Metal, but the tin content is only 40%. This may be the closest match acheivable but I'll wait to be corrected by my esteemed colleagues.