I did measure the current coming from my Beck device. It's 1.6 mA (1600 uA) - I can handle this for 2 hrs continous and I have no holes or even scars on my wrist.
Yes, it is 2x times less than Bob suggested, but (at least for now) I cannot handle more due to the unpleasant "tingling".
You may construct your devices even from 1970, it does not matter - you just made a mistake somewhere on your way.