I've got one of these:

http://ecx.images-amazon.com/images/...EL._AA300_.jpg

Technically it's a Gardena Turbo Drive Sprinkler on a Spike 36849-6.

I've got the top grey section separated from the lower orange section,
but I don't know if the top grey section (which appears to be composed
of 3 separate pieces) can be taken apart without breaking it.

This sprinker rotates fine in one direction, but stalls when turning in
the reverse direction.