Future Retro's 777 is like a TB-303 on steroids. 2 oscillators with Sub Osc. Flexible filter section with 2 slopes & widely tweak-able resonance. This one has the R3.00 operating system.
For full details on the tweaks available, download the manual from future-retro.
Vintage Synth Explorer gives it 4 stars. See their review and user comments at vintagesynth.
I've owned it for over 10 years, but I've only used it for a few hours. The last 7 years its been in climate controlled storage along with the rest of my studio equipment. I've hooked it up & put it through its basic paces. Everything seems fine, but it's probably time to put in a new memory battery (CR2325). You'll want to do that after testing it yourself. Then you can start from scratch with new patterns & songs of your own or load the factory stuff from the SySex download.
Cosmetically the synth is in very nice shape, with no major scratches or rubs. It will be double boxed with lots of bubble wrap for safety.