On Tue, 24 Apr 2018 03:10:35 +0200, Emanuel Berg
wrote:

I have an old combination spanner which on its
closed/ring side has an opening that has six,
and not twelve sides as we are used to.

Safe for clearance, are there any plus and
minuses to this type of tool as compared to the
"12s"?

Generally speaking 6 sided wrenches are either the cheap wrenches or
those designed for really high loads. High loading as the 6 sides fit
the hexagon bolt head or nut more closely and cheaper because the
broach used to make the 6 sided hole are cheaper to make.
--
Cheers,

John B.