Well firstly, my apologies.

Although I am still sure this lock is a Schlage, the construction is slightly different to what I posted. Here is a pic of the knob construction (which uses screws)...:
which was confused with the knob construction below (which does use split pins)...:
Here is the underside of the shell, showing the stamping marks which hold the loading plugs, and the 'N' or 'Z':
Still had a hard time re-picking this lock though, so decided to shim from the rear. Big mistake...due to very tight tolerances between the plug and shell and difficulty shimming security stacks 5 & 6, the shim (pepsi can strip) fatigued and snapped flush with the rear of the cyl with stacks 1 & 2 still to go! Luckily, hard tension with a wiper blade tension wrench allowed picking of stacks 1 & 2...Phew!
A new chrome plated, solid steel follower (made from the piston of a gas strut which holds up a tailgate) was able to push out the plug/shim...See bottom of pic below:
...much easier than trying to use the usual coiled Pepsi can follower.
Also, just completed is a carbon fibre follower (see top of pic above).
This new follower was turned on a lathe from a broken golf club shaft, which is hollow and tapered. (please don't go breaking Dad's Pings

) The outside taper is reduced to 1/2" along the length and a plastic plug is inserted & glued, to facilitate the notched "business end". The hollow centre allows storage of spare pins/springs etc. and a second removable plug is used to cap/gain access. (note split pin glued into rubber bung)
Regards,
Mick.