UNSAFE: Decorative use only!
I acquired a pair of these on eBay from Deb Sardone in 2018.
Each of these is 91 mm. tall, 68 mm. wide, 9 mm. thick, and weighs 72 g. The devices are not flat, but bowed. Without the bow, they are only 8 mm. thick. They are made from eitherr cast iron or forged steel. The two are closely matched, indicating that they are probably not hand forged, at least not without a die of some sort.
There are no markings on this device.
The seller provided the following description:
"These items are from an antique auction in Kutztown Pennsylvania. I am unsure what they are exactly. They are a nice heavy weight - 2.5 oz each. They could be used as a nice decorative piece for a climbing enthusiast."
I don't know exactly what these are. My guess is that they are some piece of harness hardware. Kutztown is Amish country, adding some plausibility to what is otherwise nothing more than a guess.