I was reading on wiki how very early Yugo AK's had an actual bolt hold open device. Does anybody have any pictures of this bolt hold open device or how it worked? Thanks.

M64s had/have a BHO lever installed in the receiver that is actuated by the mag follower.  Unmodified M64s can only use M64 mags.  Pics courtesy of Turbothis:




 

Thank you for the pics. I guess it was a failed attempt at trying to add a bolt hold open to the AK.

I wouldn't call it a failure since it worked pretty good.  More like an idea that never caught on.

It could only use M64 mags which would be a problem if a soldier were to pick up a mag from the enemy's AK rifle.

Agreed.  A major reason it was never adopted I suspect.



 

I knew it.  I just ordered a bunch of Yugo AK mags (BHO) and one had a cut out on the side that looked like it was some sort of bolt catch function.  While the AK is superior in many things compared to other assault rifles (I have a Yugo in 5.56 because it's easier to clean than my ARs) a bolt catch would make it more desirable.  I think the pictures are great, but unless you have seen the mags you probably could not imagine what they look like.  Unfortunately I have not gotten a full membership yet and therefore cannot post pictures, but if some one wanted a picture of what one of these mags looked like just let me know.  

M64 mag with BHO lever notch:




Edit: Now that I am home from work, I can throw some better pics up.






















 

Interesting.