Mesh screen .049 Cox engines

Do what Marleysky says.
Heat the cylinder up and then I would use the glo plug wrench on the glo plug and see which comes loose?
If the glo head unscrews then remove it and then file flat spots on the cylinder to where the Cox wrench fit the cylinder.

They probably assembled the screen over the cylinder then screwed the glow head into the cylinder, then screwed the cylinder into the crankcase and tightened the entire assembly with the wrench on the glow plug.

Then it was your problem to get the cylinder off, because I think the glow plug will come loose first. (any bets?)

That is what I would do.

Here's another recipe, Bob(like you need one).
1. Heat the glow head(to expand and tighten it to the cylinder)
2. Heat the crankcase(to expand the case threads)
3. Try the head wrench to loosen the cylinder.
4. If necessary, try the inverted canned air trick.
Chilling the cylinder tightens it to the head and shrinks
the cylinder in the case. Got to work quickly to beat the
heat migration between parts. If all fails, hit the cylinder/case
threads with some sort of penetrating oil while its hot, and try
again tomorrow. If the head comes lose, you're probably going
to have to try the leather strap, or your choice of cylinderectomy.
  I envy you Bob. I've never faced this challenge.
Good luck,
  Bob

Cool you got one coming , i have i think two of them and have sold about the same till I realized I should keep some for ME ! lol Maybe you want have to take the cylinder off ?!