Old brass key hole for skeleton key

[Southern Brass]

Found this old brass key hole plate today at an old home site. Just curious if anyone might know approximately what time period it was used or possibaly what make. As you can see in the picture it is a tad bit bigger than a quarter. There is nothing stamped on the back side . Thanks .

 

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[dig kzoo]

Neat find, age is difficult as they have been in use and made for so many years.
I have one like it from the late 1800's that was a "high security" keyway.