Portal 2

[Wiffles]

OK heres a rational explaination why they didnt sell the portal gun back in the day.. it basically peeled off your skin if you tried to enter it, because a proper portal conducting surface wasnt invented yet... as heard from the audio clips

This was before they invented the Conversion Gel which I assumed they use it to paint their test facilities with too.

Still, they had a portal gun (bulky) and conversion gel back in the 80s. This was also when cave Johnson was terminally ill (due to the convesion gel), so I guess they werent able to market it properly. Carolyn, the new owner of the company probably didnt know what to do with it either.