via this auction
Just when you think you've seen it all, something like this pops up. I've never seen one before. Note this 3M was a small Italian brand and not the huge 3M manufacturing company that many of us are familiar with. Below are some details pulled from the auction. If you know more about the unit and the brand, including whatever happened to them, or the people behind the brand that may have gone onto other companies, please let us know! This is an interesting bit of synth history that was unknown to me until now.

3M - Model PFV3
Item was tested and is in perfect working conditions

The three buttons of vowels allow you to have Vowels 1-2-3 on output (A), an analog and hot effect type of variable Voice Choir; 1 is the Aahhh , 2 is the Oohhh and 3 is the IIhhh. Then there is the parametric filter, with three pots, with the typical formant parameters F1, F2 and F3. It must be said that the parametric excludes the vowels, as well as the bypass excludes all, then only one of the effects is used, and not all together. The item was made by 3M, an Italian brand based in Portorecanati. It was produced invery small numbers. The 9 volt battery was replaced by a techincian and it will last years. In the base is a hanging to insert the processor in a bar."