The piece below the 2 chains looks to be a blade from a "flail" or"mot" mower. I've changed many many of them as our mower has almost 200 of those on it. I would date it post 1945-present. Other than the R.R. spike, I can't really tell without close up pics. Welcome to T-Net!
Oh well .. The ones that seem to be among the most popular were made by Gem Manufacturing Company from Pittsburgh, Pennsylvania. You can try researching that and see if you can find anything that matches.