Tunes your guitar (etc), but hears all the strings at once to tell you what your problem really is. It started with your Dad, you see.... Also, it has a switchable buffer. Personally, I always switch myself to be as buff as possible.

Model: TC Electronic Polytune 3 
Made: Thailand, recent model
Serial: S191202554CM0
Type: chromatic tuner
Power Input: standard 9v DC centre-negative (supply not included)
Accessories: none

Condition notes: used, no major marks. Tested and fully functional.
Overall: very good condition (8/10)