I don't understand.. What do you mean stuck together? I see 2 separate items. Can you explain what you have found a bit better?
Oh I see.. Your title is very confusing. Keep your titles short and give your explanation of what you see in your opening post. Looks like a blank metal slug.. Not a blank planchet.
I could also be a electrical box knockout. They just happen to be very close to the size of a quarter.
My first thought was the same as both of ya'll. A slug or a knockout. I'm looking for a sign of the small tabs that would be on the edges of a knockout, but I'm not sure I'm seeing them. Maybe one.
Please post full size photos, not thumbnails. Make sure you post full obverse and reverse, in focus, properly orientated and cropped pictures to get the best response to your question. Close up shots of specific areas you have questions about.