What a difference a single suffix letter can make, in this case an "L". Based on the ordinary FP3, the front face of the miller had, instead of a vertical T-slotted surface, one set at an angle of 45°. This arrangement allowed both larger and heavier jobs to be accommodated, although it did mean that three different tables with angled bases were required - fixed, universally adjustable and supplementary.
In addition, instead of the 'knee' moving, this was fixed and all tool movements made using the 'rear column' to travel vertically and longitudinally and the head to move in and out.
When used as a horizontal miller, the usually fitted long-reach ram-mounted vertical head could be pushed to the rear when its drive was disengaged. This head had three end fittings available: single swivel, double swivel, and a self-motorized high-speed double swivel. With the 'standard' head pushed to the rear, four other heads could be mounted: angular spindle, slotting, precision boring, and grinding.
The writer having only encountered few examples of the FP3L, it must have been a type limited in the number manufactured - and, when fully equipped, very expensive..