Mystery disc

[Twobit]

I stopped by a small town park where I live (it is one lot wide and goes back a ways following a stream) which, as far as I can tell is close to where a bank sat 150 years ago. Five minutes into it I was. Heckling out around the base of an old tree and got this hit on the Ace350 coming up as an aggressive ping for a penny. About 4-5 inches deep I found this thing. I have no idea what it might be. It seems to be machined pretty precisely and is the size of a quarter, maybe a touch wider. It is not ferrous.
Any ideas?
4027340274

[The Rebel]

Top part of a C battery?

[Full Metal Digger]

Definitely the upper assembly of a henway!

[Twobit]

Back in the days when I worked in the trades we explained to the new guys that the problem was a broken dikfer. The henway thing is definitely more kind.

the answer was always, "didn't your parents have "the talk" with you yet?"

[OregonVic]

Looks like a part of a pop valve. Probably had a spring on the one side.

[Twobit]

That's about the best answer I can imagine. Appears credible...of course, I had to google "pop valve" to get an idea! Thanks.

[Digger Don]

Back in the days when I worked in the trades we explained to the new guys that the problem was a broken dikfer. The henway thing is definitely more kind.

the answer was always, "didn't your parents have "the talk" with you yet?"
As obvious as it is, He got me with it. One of these days I'm going to go on a hunt with Daddy Digger. And when I do, he might just find a round piece of aluminum with the words HENWAY on it. :devilish:

[Twobit]

Don, I read that thread. You get the credit for showing some doubt before daring to ask! It was pretty funny. I think that you might want to surf on over to http://www.coinsandpins.com/custom-coins and order up some henway coins. They'd make a sweet forum gift!