The photos here, show the lane marker before the covers were fitted. There are 59 tubes on a chain, the chain is driven around by a rod that comes off the nearside track sprocket hub, the rod pushes a pawl lever on the driving sprocket of the marker. Look at the close up photo and you will see a short rod sticking out, this was where it had been cut off on removal from the tank. So, every revolution of the the track sprocket, the lane marker pawl moves. When one of the tubes is in line with the end, a hammer falls, the hammer having been riding up a ratchet ramp above the sprockets, again look at the close up. The hammer hits a firing pin in the top of the tube. Under the cap in the tube would be a blank .303" cartridge and up inside the tube, a marker post, which is telescopic and with a thin probe on the end looking like a hypodermic needle. The blank fires the post out and as it does the post extends as it is fired into the ground. This is timed to happen every 50 feet.
From the controls, the marker can be selected to fire left or right. Normally two flails would work together, so the left one would mark to the left and right flail mark to the right, giving a lane through the minefield wide enough for safety. When the control is in the Off position it in turn operates a cable from the marker to the tank drive sprocket, which disengages the rod operating ratchet.
All of this equipment and the rest of the vehicle was in an advance state of decay before restoration.