Hello Raphael.
I have some zipped BMP image files of the FB2 manual, in which the rotary table is well described.
The images are not great, but are legible/usable.
PM me with your email and I will email them to you.
The 'Lock pin' you speak of is used to 'pin' the rotary table in fixed indexes – if I remember correctly – in 15degree increments, in the perimeter of the rotary table. If using the index discs or dividing plates, that lever is pulled out and rotated to the disable position, so that you can index incrementally. The other two levers are to lock the table in position while machining.
To turn the table freely, loosen and back off the Cap Screw seen near the worm shaft exiting the table block. Then rotate the worm away from the table gear by rotating the dividing plate counter-clockwise.
Joe
fix typo
Edited By Joseph Noci 1 on 01/12/2019 20:25:17