The only information that I have been able to find out was that the tanks are from a pre-production test run, and were never released. Because of this, there is no retail packaging, and the tanks are sold in cellophane bags.
Although the models were discovered in a warehouse in Hong Kong, I believe that they were made for a Japanese company. I was told that there should be 8 tanks in the complete set, which seems to fall into the typical paradigm that Japanese companies use to sell gashapon toys. I'm guessing that the tank I'm missing would be the "secret" model that is typical of these collectible trading toys.
The 7 tanks that I have are the following:
The models come with the two halves of the hull fitted together, but not glued. The machineguns, headlamps, pioneer tools, and other small bits come pre-painted on sprues, and need to be attached separately. The soft vinyl tracks also need to be installed separately.
I have not taken any measurements yet, but they definitely look 1/72 as opposed to 1/76. Stay tuned for size comparisons when I get these built up.