Has anyone came across this sort of low voltage lamp.

We moved into a house less than a year old and I took out what I
thought was run of the mill MR16 lamps but when I went to repalce they
fitted ok but never worked.

I checked what came out although the look identical to the MR16 GU5.3,
one was actually marked GU6.

Anyone know about these lamps and where to purchase as I can't seem to
find any.

Thanks