4 Antique solid Brass door knob plates

I got 4 solid brass door knob plates off of a french door. They are roughly 6 inches wide and weigh 5 to 10lbs each and on the back F25 is stamped on it. I haven't been able to find out anything about them online not even a picture yet. What I'd like to know is around what year they were made. The door knobs them selves looked like brass but when I took them apart it was steel on the inside and had Phillips head screws holding it on the door so I don't think they are a century old but I'm wondering if they could be from the 50's or 60's. If anyone knows anything about these I would greatly appreciate any info you might have. You can msg me on here or my email which ever you prefer. I did some more looking and I think it could be a mid century Starburst door knob but I still haven't found a pic of it yet but they look very similar to some of other Starburst door knobs.