Valuation: prog with comp slip signed by Tharg

[slithy]

In my collection I have a copy of prog 189 with a comp slip fixed to it with a paperclip. I don't know what the story is behind this. The comp slip says:

ipc magazines
with compliments

Tharg (signed in green felt-tip pen)

Then the address at King's Reach Tower

Is this worth anything (beyond the value of the prog)?

[Leigh S]

There will be trace thrill power in that clip!

Hard to put a price on it I suspect - I imagine a distraught Earthlet wrote in to say he had missed his regular prog and Tharg swooped to the rescue- might even be a letter about it in a subsequent prog!  How did you come by it?

[slithy]

I bought a collection of 2000ADs on Ebay and this was included. As I remember, the seller was a relative of the original owner who was clearing out their stuff, so they didn't know anything about it.