Ghost,

The CS can be easily spotted as it has a flat-bottom profile to the case whilst the original Ollie has that characteristic rounded "under-belly."

I have some friends in the UK who fly nostalgia C/L combat and mix the CS engines in with the originals. They say they run about the same.

Also...you can get the CS Olivers in the US for a lot less than in the UK.

My friend from Scotland was over here a couple of years ago and mentioned they were around $120.00 each and it took six months to get one. I made a quick call and we ordered three of them at $65.00 each and they were here in three days. Sure flipped his kilt over the price and availability here.