unknown optics

[Franzi]

Hi, what is this? marking: bek+ 3x8 Thx

[pzo]

Optical sight

Most probably this is PaK 75mm or 88mm telescopic sight. I have also seen one marked with FlaK.

[mlespaul]

Yep,
its the standard 3 x 8 anti-tank telescope.

If the reticle is 3 marks (one big triangle w/2 little upside-down v on either side, it goes to the 50 mm Pak 38 using the Zieleinrichtung 38 or the 75mm Pak 40 using the Zieleinrichtung 38.

If the reticle has the 7 marks (one big triangle with 3 little upside-down v on either side, it goes to the 75 mm Pak 40 or larger using the Zieleinrichtung 38A or the 8.8 Pak 43/41 using the Zieleinrichtung 43 S.v.o.4. (or larger caliber) as pzo said

OR

as the ground target telescope for flak guns of 38 cm or larger, but those usually say "Flak" along the side, but not always

You can often go by the dovetail groove assembly size and position along the tube body along the bottom as to which gun platform it went to.