Super rare and highly sought after, pre-Clyde McCoy, 1967 Vox JMI wah wah in Castledine grey - an original first generation model. Housed in a volume pedal casing. In great & clean 9/10 condition. All original except the two rubber front feet and screws. The early units were built with BC150 transistors (which this one has). In the later production models, Texas Instrument 2N3707 are usually seen. It's a clyde without the resistor in parallel with the inductor.

The inductor supposedly measures 250mH.

This wah has a tighter, thinner sweep. A lot less low end, more emphasis on high end and upper midrange.

The serial number is #5527 and the sticker on the bottom plate says:
VOX Wah-Wah Footpedal
Designed & Created by
Jennings Musical Industries LTD
VOX WORKS – ERITH – KENT – ENGLAND

History of the Original Famed Vox 'Grey' Wah:
Originally developed in 1966 by Vox Thomas Organ Co. in sunny California, engineered by the famous Brad Plunket with the assistance of Del Casher, the Vox 'Grey' Wah is one of the earliest and most sought after Vox Wah pedals ever made.
Often mistakenly referred to as the 'Prototype', it is clear that they were considered a production model by Vox JMI as these were advertised and sold throughout the UK (See Magazine Ad).
The most unique feature of the Vox 'Grey' Wah is the use of a 250mH Inductor which is capable of a much higher sweep than typically used today.  This is the wah pedal in its purest form as designed for the electric guitar. The 'Clyde McCoy' model that would soon follow was re-tooled for Vox's new line of electric horns being marketed for what they were sure was going to be the resurgence of the Big Band era.  Although this never occurred, from that point on, the wah pedal design remained the same and the sweep, as Del Casher put it, has never been quite right since. 
Most famously used by Jimmy Page from 1967 through July 1970 with The Yardbirds & Led Zeppelin and featured on many of his early live performances and recordings such as 'Dazed And Confused' and 'How Many More Times'.

More info here: http://www.voxsupreme.org.uk/vox_wah_wah_pedals_1967.html