Interestingly, the sockets all have just the D - I -, but the ratchet, breaker and sliding t, all have Duro-Chrome and I do not see any marking on the extension.
Found this a while back at an estate sale and it seems to have some age to it. I am a new member and thought I would share some pics. The last pic is from alloy artifacts and dates it to 1931 according to the logo. I haven't been able to find any else like it out there, so far. Thanks,