I have heard people saying that this pedal is based on the vintage MXR Phase 90, but it's not. MXR 90 is build with the very commun OpAmps TL062CP and this Guyatone use the NJM4558L from JRC3128C which are really more rare (like the JRC4558 used in the most wanted original BOSS OD1). Also the big difference is that there is a second pot to control the depth of the effect, like the MXR Phase 100 (but the MXR uses TL022CP). If you want to know which other phasers uses the same OpAmps as this Guyatone look at other japanese models, there are the Roland AP7 or AP5 Jet Phaser, the Maxon (Ibanez's name in Japan) PH350 rotary phaser, the Pearl PH-44 Phaser...

For the sound, words are meaning less, just listen the demo video I pasted here

This Guyatone have also a trim pot inside that let you change the range of frenquencies that the LFO will travel, depending of the sound you want to us with if not a guitar.

I regret you can't choose the shape of the LFO, it is something between triangle and saw. Longer rise than the fall, but the fall isn't vertical like a real saw. Anyway this pedal doesn't have many controls due to its size, but the sound is very cool if you like analog vintage style.

Under the pedal, the serial number sticker is missing but the Guyatone logo is written at the bottom so the serial number would start by 93,94 or 95 which means this is the first edition. When the logo is written on top, the serials start with 98 or 99, those are later editions.

Mine works perfect. The rubber around the unit isn't cracked like most of this units of this serie.