The bolts were used to fasten two pieces of rail together. It had a 4 hole rounded plate with 4 holes in it. Two on each side. Where the washers went as well. The plate is just marked by size and looks like Rail road co. I worked for Southern RR and L&N. Started on the tracks later became a track foreman then a bridge carpenter and then an operator running heavy equipt like buckrus erie cranes,dozers and high rails. The log or tie handler was the most fun. Traveled all the way from Tn to Chicago 15 miles at a time. Did it for a few years then moved on...

Nothing like the ring of a hammer on steel.