That little penny trick was all about psychological nudges long before we had points systems. If you look at the ledger, the shopkeeper had a simple formula—add a penny every five pounds spent, then double it if the customer made a repeat purchase that week. It’s essentially a discounted return on investment in the same way modern loyalty programs pay you a small bonus for each dollar spent, but without the tech overhead. The math isn’t much different: you’re just giving the customer a small incentive to keep coming back, and the shopkeeper keeps the math tight to avoid over‑spending on the freebies. It’s fascinating how the same principle underlies both eras.

I’ll take a look when I’ve got the ledger in front of me. The math is neat—just a few basic ratios—and it’s exactly what makes those old shops thrive. If you have the numbers, I’ll run the numbers for the break‑even point and see how it stacks up against today’s programs. Thanks for the offer, it’s always good to cross‑check history with modern data.