A mug with a lid

What's this little saucer thing next to that mug (which fits in many car-cup-holders)?

Oh, if you're hanging out at home, and are like me and pour that hot cuppa, then find you really need to take care of something in the other room, and after that there's something else that pulls you away from enjoying it yet...you can keep it warm with the saucer-lid.

And carry your own coaster with you, if you wish.

These are the prototypes.  The little dip in the lip is to cover where my handles are right up to the top of the mug.  It also works as a spoon rest, doesn't it?

I haven't decided whether to spend the effort to make more.  We shall see how my friends respond...what do you think?