By 1988, Hasbro were done with rainbow ponies in most places.
The last Hong Kong made Rainbow Pony set seems to be this one. I
use their German set name here because it's how they're
distinguished online - but in truth it just means 'Rainbow Pony',
and all Rainbow Ponies sold in Germany were sold under this name.
We should see this set, therefore, as a continuation of Rainbow
Ponies past.
Because the set includes versions of some ponies sold in other
places, it is sometimes mistakenly put with 1985. The backcard is
dated 1987, as is the insert they appear on. But this insert
includes ponies advertised in German promotional material in 1988.
(A similar thing happened with the UK insert for the same year,
which is also dated 1987 but features ponies on sale from 1988).
The deciding factor is the design of the card, which has the
coloured border and art style used in parts of Europe (including
Germany) in 1988. It also has the updated font on the rainbow,
which came in in 1988. This means that we can date this set
confidently to 1988.
Hummelchen Mint on Card Germany, 1988
The advert above at the top of the page comes from a German
promotional booklet from 1988. You can read the full advert here.
You will notice that the name Himmelstürmer is listed here, and
this seems like it might have been a production name - the pony in
question was ultimately sold under the name Himmelstänzer
(Skydancer or Heaven Dancer).
There are known variations with this set, predominately relating
to the size and/or colour of the symbols. Smaller symbol ponies
often show up in Austria, but whether this is uniform or not is
unclear. (Both my Nachtlicht and Regentropfen came from Austria).
Smaller symbols may also relate to the timescale of release or
other production changes.
Ponies in this set also often have strange feet! Aside removal of
the Pat Pend stamp (which is fairly standard in German pony
releases by 1988), some also have other odd footprints and bits
smeared out. I have no idea why, but this is so common in this set
that it's considered a normal quirk.
These ponies had painted or metallic painted symbols, rather than
glittery. This was the case even with Mondschein (Moonstone) and
Hummelchen (Flutterbye),
who were the 'hangover' ponies from previous sets - both were sold
in Germany in 1987.
The inclusion of versions of Skydancer and Starshine in
this set may also have been intended to close previous 'gaps' in
the previous Rainbow line, as neither of these characters were
included in the 1986/1987
European Hong Kong sets.
Regenbogen-Ponys (1988, Germany and Austria (possibly
Switzerland)