Thanks to Carol Gingell for permission to use the following pics of her Shadow Echo. I believe the Shadow Echo used 2 valves, instead of the 3 found on the Mk II, and was probably made around the late 1960s but I can’t be sure of this.

Thanks to Brian for permission to show this pic of his Shadow Echo unit. As you can see, this one has the grey fascia and I suspect it may be later than the blue fascia example shown above.