Interesting idea if made for McDonnell Douglas. I am not sure if MD had a plant in Canada although I only live 40 minutes from the Minnessota border. I have on a few occasion brought used tools home from the US when traveling.
I agree that they are some sort of specialty socket. It is interesting that they have the same hole diameter and both use 3/4" wrench to turn them although the longer one is 9/16" and the shorter is 3/4". I would have thought the sockets would be scaled up proportionally. Well made sockets and...
I have two sockets with 1/2" through holes where the square ratchet drive opening would be located. You turn the sockets with a 3/4" wrench. One is a MD-12433 (longer one) and the other is MD-12362 (shorter one). The MD-12433 appears to have the end turned down for approximately 1 1/4". Probably...
As others have said this appears to be a beam clamp for hanging pipe. They clamp onto the bottom flange of a Wide Flange Beam or an I Beam. ITT Grinnell and Anvil catalogs are on line with similar clamps. The heavy duty beam clamps from Anvil can use up to 3/4" diameter threaded rods and hold up...
Looks like a Central Tools, Inc. micrometer. I believe they are still in business and sell mostly to the automotive repair shops. Same finish to the micrometer, same protective sleeve, same yellow box and instructions.