My guess would be a handle that you could attach to a Pyrex baking dish to remove it from a hot oven.
This one looks like an early version. I inherited a couple of these from my Mom that actuate the dish’s tab clamping action by turning the end of the handle.
This one looks like an early version. I inherited a couple of these from my Mom that actuate the dish’s tab clamping action by turning the end of the handle.