1800's Brake Shoe identification

Hello all. I found a brake shoe on the side of a walking path that was the rail alignment for the Orange and Alexandria railroad during the Civil War. There are numbers and letters on the side which read O 313

Does anyone know what this might refer to? Part number? Manufacturer number? Train Car number? Any help would be much appreciated.

I don’t know how to attach a picture. Sorry.

Find a 3rd party site to post the picture. Then use the link to the picture from that site to post the picture here.

Printed discriptions of antique items don’t discribe the items adequately. Pictures, Pictures and more Picturs - unless one can view the object in person.

Hopefully this helps. Thanks for the tip on adding pics.

Helps some. However, the pictures aren’t large enough to view the details sufficiently.

It was probably made by a local foundry or at the Railroad shop