Mystery 22 Conversion Kit

[rcathey]

Hello all,
I was hoping you knowledgeable fellows could help me out with a bit of a mystery.
I picked up this kit at an auction this weekend. I know it's a 22 conversion kit but I haven't the foggiest what it's for.
The outside dimension of the barrel is 8.8mm so I think it's for a 9mm.
The machined aluminum section has a groove cut in it so I think it slides over the existing front sight.
The clamped band around the machined aluminum section would then serve as a front sight...I think.
Both the shell holder (which contains the firing pin) and the chamber end of the barrel have a 10 engraved in it. Electropencil, looks like.
The box is nicely fitted sliding top box out of maple. The top slides very snugly.

Any ideas?? I really appreciate it.

Information

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[rcathey]

Couple more pics:
Attachment 86549
Attachment 86550

[Patrick Chadwick]

Measure the "in barrel" length carefully - my guess would be it's for a Luger.

[rcathey]

Alright, I took a few measurements:
The barrel measures exactly 8.25" when including the shell holder. Put in other words, if a barrel measured 8.25" from bolt face to muzzle, it would cover this assembly. However, note the two lock nuts -- with these included, the barrel could be, at most, 7-13/16" and, at least, 7-5/8". I suspect these nuts would essentially be used to adjust headspace.
The machined aluminum section measures 4.25" overall length. The opening (which I've presumed to fit over the existing gun's barrel) has an inside diameter of .597".

[browningautorifle]

There's a marking on the biggest round, what is it?

[rcathey]

I can find no markings on any of the parts except for an electropenciled "10" on the shell holder and the barrel.

[browningautorifle]

Look at the top picture, you'll see what I refer to...

[rcathey]

I believe I see what you're seeing. Nearly in the middle of the biggest round section? That's just a couple small scratches...definitely looks like it could be a hallmark in that blurry cell phone pic though, haha.

[rcathey]

Thought I'd add in some more photos. May be helpful to someone else someday even if we don't figure it out now!

[rcathey]

HA! I found it! For some reason it dawned on me to Google not for "22 conversion kit" but for "22 subcaliber conversion" or something along those lines. Looks like it's a Leinhard System conversion kit. Check this out:
Lienhard 4mm for the Swiss 7.5mm rifle - General Ammunition Discussion - International Ammunition Association Web Forum
Do a google image search for "kleinkaliber einsatzlauf kaliber" and you will see quite a few pictures.
Unfortunately, I haven't found tons of information and thanks to Photobucket's stupid new rules it's hard for me to match the information with images.
I can't find any of these that have sold on eBay or Gunbroker. My search continues but now in a very clear direction!