Thanks for the info David.
I've tried that sequence a couple times this morning, but no dice so far.

My father had written it down:
5xL - 1st #
2xR - 2nd#
1xL - 3rd#

Which obviously wasn't working. I know when I DID get it to open the One time, weeks ago, I was experimenting with # of turns BOTH ways (LRL and RLR) - so it very much COULD have been RLR (as you said) that worked for me that once.

I'm trying, as You advised:
4xR to 1st # (Passing "0" 4x, and stopping on 1st#)
3xL to 2nd# (Passing 1st# 3x, and stopping on 2nd#)
2xR to 3rd# (Passing 2nd# 2x, and stopping on 3rd#)
Slowly turning Dial back to L (Listening for click & feeling for dial stop)

I've also tried / incorporated:
- The above exact sequence reversed (LRLR)
- Doing both of the above sequences while jiggling the door and/or bolt handle while giving the final (drop) dial turn, and also tried shimming the door with folded paper to put slight inward pressure to create a neutral hang, should anything be leaning outward against it from the inside.
- Pre-rotate dial in direction opposite of 1st sequence turn, a minimum of 4 times before starting sequence

No luck so far.

Very frustrating, as I KNOW the numbers work - otherwise it wouldn't have opened once.
I feel like there must be SOMEthing very simple I'm overlooking.

Any ideas what I could be doing wrong, or something I've misread? Does anyone out there have a Pillards No 19 to try / confirm the turn sequence on, etc?

Thank you in advance for any assistance.