Olympus Turret

BH, BH2

These use the same horizontal linear dovetail turret:

However, be warned that BH (always?) uses 25 mm (M25) Neo finite objective where as BH2 uses 26 mm (M26) infinity corrected objectives. Here is the underside of a M25 turret, note that they both look the same:

From what I understand, the 25 mm objectives will fit into a 26 mm turret but 26 mm objectives do not fit into a 25 mm turret. Here is a 26 mm turret:

There are also RMS turrets:

for which you can get plenty of finite objectives and even some infinity such as for MSPlan. Note that all of the RMS turrets are BF while most, but not all, of the M25/M26 turrets are BF/DF.

BH3

Unlike earlier BH, the BH3 is motorized and uses a larger vertical linear dovetail. I was able to take the 5 position revolving part off of this and transplant it onto BH2 dovetail to make a BH2 compatible.