I'll through a couple of educated guesses on it. From the handle pattern, I think it is a British Tech.
Blowing your picture up, I am not seeing any date code (single letter lower left of top half of blade guard underside, with corresponding number 1-4 on the right side). If I'm correct that there are none there, it's 1950 or earlier. The 4 slots in the blade guard have parallel sides, instead of forming a slight triangle, which was changed sometime around 1945. So I'll say '45 to '50.
Your aluminum Gillette Tech was made in the late 60's and early 70's, I believe. I had one, but didn't like the light weight, so I gave it away. Mine was made in Canada, I believe, but they were also made in England. I don't know if the Aluminum Tech was also made in the US.
Actually, I have both varieties of this British Tech in both aluminum and steel. The date code is on the inside of the head. I'd look them up but I'm moving and they are both in storage. Also note that the later versions have the Gillette logo embossed on the head rather that etched.