Well.. I had on my hand yesterday a MVVS gas 26 with the blue head ... but that's not really important. What it's important for me is to know if there is any way to distinct an old model from the new ones. I have found one engine with the neutral head in a shop. I'm thinking on buying a new one, but I don't want to buy the old version. Is there any way to know if it is old or new version?

Thank you.
Regards,
Javier