We have a few FRAIM padlocks with four rivets (two top and two bottom) and "FRAIM" imprinted on both sides, thought to be from the 1890s based on where they were found. They are 3" in size and relatively common. FRAIM began business in 1881, and after the turn of the century partnered with other lock manufacturers including Slaymaker. Try to find a copy of THE PADLOCK COLLECTOR by Franklin M. Arnall through your library (several editions) - this book has photos you can comopare your lock to. John Sapanara, Pascack Historical Society, Bergen County, NJ