Hello,

I recently purchased a house built in 1948. When I attempted to install my dryer, I realized the outlet was 3 prong 250v. A helpful post said that I could convert this outlet to 3 prong 240v. I have looked a little closer in the outlet and noticed there are two hots (red and black stranded) and what looks like some sort of stranded copper clad wire (the outside looks silver while the middle is copper). I have two questions:

1) Does anyone know what type of wire this is, and will I risk rusting a connection to a new 240v outlet?

2) What tool should I use to test if this wire is actually a ground wire (which I'm assuming it is) -- the access to the area under the house where this wire leads is very difficult to get to, so following it visually to a water pipe would be difficult.

Thank you.

What you need is NOT 250v. What you need is a 120/240v circuit, and that IS what you have.
Older "3-wire" dryer and range circuits were two hots and a neutral, with no ground. The neutral also served as the ground.

The cable you have there is type SE-U cable, and it was fine and legal for this application. That cable is the only cable where the neutral was bare.

You are fine using this circuit. Just get a dryer cord to match the receptacle.