The method should work universally. I worked this out for myself, but I'm sure I'm not the first to think of this, the concept is quite obvious, once you can visualise how the lock works.
The lock & how it works (consult the patent linked near the end for more diagrams) :
There are Banham cylinders that are standard pin tumbler mechanisms. This cylinder is quite different.
The lock's key has two parallel rows of 6 dimples, but unlike most dimple locks, this lock doesn't use driver pins & key pins. There are 6 pin pairs, and the key has two rows of 6 dimples so that it is reversible.
Instead of using key pins & drivers, the lock uses pairs of horizontally opposed pins.
There is a hole drilled for each pin pair through an outer cylinder(housing), through the plug & out through the other side of the outer cylinder. The keyway runs longitudinally down the plug, as with a regular pin tumbler lock.
Inside this hole are a pair of pins, of different lengths to each other & their total combined length is the same as the diameter of the plug. The pins each have a spring & are biased inwards, towards the centre of the plug. The tips of each pin pair touch each other in the keyway. There are six pairs of pins arranged in a straight line down the keyway.
When the lock is in a neutral position (no key inserted), the longer pin of each pin pair is protruding from the plug, into the housing, across the shear line, preventing rotation of the plug.
The correct key moves each pair of pins so that they are both inside the plug, clearing the shear line & allowing the plug to turn. Since the total length of a pin pair is the same as the plug's diameter, the dimples in the key must run all the way through the key, allowing the tips of each pair of pins to touch eachother.
An image of a cross section showing the plug, housing & a pair of pins at rest (no key inserted) :
An image demonstrating how a correct key(top) & incorrect key(below) positions a pair of pins :
If we imagine a lock with only one pair of pins, under tension the longer pin that blocks the shear line will bind & the other shorter pin will remain springy. This is how an unset pin pair feels.
To pick this pin pair, use the tip of a pick (I use a hook) to depress the springy pin from it's edge - if you press the pin from it's tip, the thickness of the pick may prevent the binding pin from retracting far enough into the plug.
Depress the pin as far as it will travel. Now decrease the tension on the plug until the binding pin is pushed by its spring back into the keyway. Gently bouncing the tension once should achieve this. Reapply tension & release the pin you were depressing. It will spring back until it touches the tip of the other pin. The pin pair is now set.
If you now apply pressure to each of the pins in that pair, you should find that neither of them wants to move, they are now trapped in the plug. This is how a correctly set pin pair feels.
To pick a fully pinned lock, apply tension & feel the pin pairs. Both pins of a pair that are not binding will be springy. Find a pair that is binding, pick it as described above & move on to the next binding pair, just as you would with a normal pin tumbler lock. Keep going until the plug turns. It is not very difficult, at least with my lock. I was able to pick my lock easily after only having the lock for about 24 hours. I have quite a lot of picking experience, but my skill level is nowhere near that of some members here!
A few tips :
To simplify things whilst getting familiar with the feel of binding pairs, pairs not binding yet, pairs that are set & the manipulation of pins, I initially used the lock's cam to apply tension. Once I got a feel for it and had verified that my concept worked & that I could pick the lock this way, I moved to using a tension wrench.
Sometimes a binding pin will not spring inwards when the tension is released, in these instances, you need to manually counter-rotate the plug ever so slightly - enough to unbind the pin, but not enough to disrupt other pin pairs that have been set already.
The tools I use are a Peterson prybar & a Peterson hook. A half diamond or a flag dimple pick should also work very well. If I owned dimple picks, I would've started out using a flag.
I hope I've explained this clearly enough for others to test the technique.
For those wanting to see drawings of the guts of the lock, the patent for this lock is here : http://nynex.s5.com/lp101/EP0892130B1.pdf
The patent asserts that picking the lock would require a tool to pull binding pins back into the plug & that this would be difficult. I agree with the last part of that statement & if the lock was improved to achieve this, then it would be more secure. The addition of a thin lip to the end of each pin (like one end of a shallow spool) would probably achieve this. Countermilling the chambers would help, too.
As it stands, I feel that this lock is mostly relying on security via obscurity.
I'd be very interested to hear how other members who have a Banham lock of this design go with this technique.
Finally, a big thankyou to MrAnybody, I'd never have had this lock without him!