Photo provided by Hank Zaletel
License: Creative Commons Attribution-NonCommercial-NoDerivs (CC BY-NC-ND)
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BH Photo #244614
After fiddling with the image a bit, I'm thinking 1886.
The first digit must be a "1".
The second could be either an "8" or a "9". I'm pretty sure I see a line that's slopes from the upper left to the lower right - making it an "8".
The third seem pretty clearly an "8" to me, with a line crossing in the center.
The fourth digit has a curve to the left from the top to the bottom - making in either a "6" or a "0". It looks to me like on the right the line curves in to intersect at the center making it a "6".
Here is the clearest of my "enhanced" images, cropped for just that area of the plaque.