I noticed this for the first time while comparing the BR 110 from the 26512 train set with prototype photos: the pantographs are mounted the wrong way.

This applies to double-arm pantographs with two wipers:
With E 10 and E 40 (i. e. 110, 140, 139, 112, 113, 114) locos, the diagonal bars show to the centre of the loco, not the end. This also is the correct position of the elbow for single-arm pantographs.
BR 151 and BR 141 have them the same way.
E 03 (103) and BR 111 have them the other way around: diagonal bars or elbows show to the end of the loco.

I checked the following M* catalogues and found the following locos with reversed pantographs:
- Yearbook 2005 H0
34401 (BR 140) p. 109 (37401 on the same page is OK)
25612 (BR 110) p. 157
- Catalogue 2001/2002
39573 (E 03) p. 84
30331 (BR 110) p. 83
88687 (BR 101) p. 365 (reversed single-arm pantograph)
- Catalogue 1996/1997
3033 (BR 114) p.59
3053 (BR 103) p. 60
33432 (BR 151) p. 61
3343 (BR 151) p. 61
28503 (E 10.12) p. 87
- Catalogue 1977
3053 (BR 103) p. 20 (same loco correct on p. 25)
3037 (BR 141) p. 21 (3034 on the same page correct)

It seems that M* just don't care how they mount the pantographs.
Luckily you can easily turn them around.
I reversed the pantographs for my BR 110 (26512).

I must confess with respect to wrong and right direction of pantographs: I haven't seen all prototype locos - and strange things happen in the real world!
So if you saw prototype locos with pantographs in the "wrong" direction, please let me know!

Um,
How many rivits are on that pantograph?[:o)]

Good quiz material!