Why are Tee Dee 010 so expensive?

Here’s one that needs a little TLC. $65

https://www.rcgroups.com/forums/showthread.php?3215597-1960-s-Cox-Tee-Dee-010-engine

I thought, thanks to Ebay, that I was going to join the fabulous cult of the Tee Dee .010. It was with great sorrow I pulled out my Mitutoyo caliper, and my new jewel had all the measurement of a Tee Dee .020. Is there any way from a few simple Ebay photos to tell a Tee Dee .010 from a Tee Dee .020?

I think the most apparent difference is the diameter of the NV knob, and the diameter of the center-piece in the glow-head relative to the cylinder diameter. I guess the diameters of the 010 and 020 knobs are the same, as well as the diameters of the 010 and 020 centerpieces, but of course the diameter of 010 cylinder is smaller than the 020.

In one of the posts here on CEF a picture was posted with the 010 and 020 side-by-side, pointing to the said proportions of the 2 engines.....sorry I am in the office and cannot make a photo now.

I recently posted this id tip in the "Burned engines" thread:

The littlest Tee Dees are hard to identify if there is no size reference in the picture. But there is one tell-tale that is pretty obvious when you realize it. I didn’t realize it, it was pointed out to me. In the picture below you can see that in the .010 the collet retainer nut is about equal in length to the thickness of the prop drive plate, whereas the length of the collet is about twice the thickness of the prop plate of the .020.

Sorry about the mess all over the .020, the pic was taken before I cleaned it up. Here it is in its current state, where you can see the difference better

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Download the Tee Dee .010/.020 manual from the https://www.coxengineforum.com/h24-instruction-sheets. Compare the two drawings and pay attention to proportions. The proportions of the cylinder to crankcase, needle to cylinder, is the only way to compare when no scale reference is in the photo. I never noticed the size of the retainer, nut but that is also quite clear.

gkamysz wrote:Download the Tee Dee .010/.020 manual from the https://www.coxengineforum.com/h24-instruction-sheets. Compare the two drawings and pay attention to proportions. The proportions of the cylinder to crankcase, needle to cylinder, is the only way to compare when no scale reference is in the photo. I never noticed the size of the retainer, nut but that is also quite clear.

Greg, I had done that. I was hoping to get a Tee Dee 010 in my hands so I could compare it directly to the pictures. Instead, I got a really nice Tee Dee 020 for my money. So, clearly, my ability to see proportions was off. I am now going to use the retainer nut size, and how far the notches on the head are to the knob.

It's the Collet same size on the .010 not so on .020   https://www.mh-aerotools.de/airfoils/cox_frameset.htm look upder TDs

Based on the picture the glow head is a dead giveaway that it’s an .020. The .010 almost always has a solid top area on the glow head where the wrench engages. Also there was never any knurling on the .010 glow head. The second clue is the straight wall cylinder. The .010 never had a straight walled or stepped cylinder. The base of the cylinder was always larger than the cylinder wall.

So, this, for example, would be a Tee Dee .020 correct?

https://www.ebay.com/itm/COX-TEE-DEE-010-PERFORMANCE-ENGINE-W-PROPELLER-AND-WRENCH/123669289768?hash=item1ccb439b28:g:fTsAAOSwoOxceE8M

3" prop is not correct for that engine, note it does not match the thrust plate.
Nor does the spinner match the prop hub.

Seller is fooled by the prop on the engine. The fins give it away too of course.
It is indeeeeeed a TD .020