Have I used this tuner? It’s hard to say. It looks basically new. The pitches from a standard tuning indicated by red panels which, I assume, light up when activated. The battery, it seems is dead, but I may leave it in since I’m unsure how to recycle it in my new building yet. This is model 5006, which seems to imply a 5001, 5002 and so on, though given the irregularity of software versioning rules, I wouldn’t be surprised if hardware engineers had their own quirky systems. It’s got a frequency sensitivity range between 430 to 450 Hz, which, without looking, I assume contains the low and high strings of the guitar with some padding on either side. It was made in China. The meter shows derivations of +/- 50 cents from the target pitch.