Hi can anyone please tell me what this little spanner/ratchet extender is called, also am I correct in thinking the circled S trademark stamp signifies its Snap On ?

Looks like a torque adaptor to me. Here's the Snap-On T.A. page - one looks very similar to yours.

https://store.snapon.com/Torque-Adaptors-C796465.aspx

Quick work ! A torque adapter - it makes sense now.

Lots of folks make them, but that logo does not look like a Snap-on.

https://www.google.com/search?q=torque+adapter+wrench&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjghbniweDcAhVEYKwKHTz5B_QQ_AUICygC&biw=1441&bih=662

Yes i Thought the same the little S looks like a Snap On font

Snap on yes but for who I don't know may be Cat.

For who ? So am I to assume you mean it was made for a specific vehicle manufacturer ?

I know they made mechanics tools for Caterpillar and I would guess others too.

Hmmm, did y'all hear that snap on had a "breach" in their web site.... check out anything charged on your account or weird charges