Hi Paul, I've actually managed to get a copy of your article, and it's of definite help in this quest. As you mention, there really isn't much information on these, at least that I've been able to find. You seem to have had the same experience.
I've got queries out to museums, arms rooms, and other collectors for any more examples, or information. I'm still in the data gathering stage, but it somewhat surprises me how little information there is, out there. I guess a funnel just isn't sexy enough, lol.
I'll post up links to the paper once it's written, but any and all information is still welcome. Many thanks to all that have, and will, post information and pictures on these accessories. Thanks in particular to those of you that have taken the time to document your collectibles and post the information!
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Now, the electro-pencil is interesting, haven't come across that yet, you're the first. Possibility of any detailed pictures?