It is fairly common for the Twin Cam hand brake pad arms to have deteriorated adjusting screw parts. The riveted cage holding the square brass square nut may be corroded along with corroded screws and compression springs and damaged or missing brass huts.

You will note that the formed bracket is open sided and looks original. The nut fits in there very well once the bolt is in place. The spring is only there to allow the release of the pads from the disc. The nut is easily made if you can find some suitable brass.

You can also make a new adjusting bolt from an ordinary bolt. The head can be fashioned on a small lathe but note that it is not a countersink but a spherical shape which can be created with a file in the lathe or turned up with a created tool for the purpose.

The brass nuts are shown as Brown And Gammons part number 7H8241A for about $3.00, You may be able to find them from other sources as similar unit was used on Jag XK150, maybe others. There function is to relax clearance of pads to rotor when handbrake is released. If the springs might be a bit collapsed, you might wind them out, give them a small stretch, and wind them back into the slot again.