Old (big) mag cards?

[John Garza (3665)]

(07-08-2023 01:02 AM)John Ioannidis Wrote:  If/when I find them, I'll "develop" an HP-67 card and post the results.

I think this was done decades ago by the PPC group. And at the time, while I had no special chemicals, I did have a jar of iron filings from my old chemistry set. Worked just fine - you could see the tracks on the card. Just be very careful cleaning the filings off the card if you want to use it again.

-J

[HP: 9100B/9815A/35/45/55/80/70/65/67/67T/97/97S/91/92/21/22/
27/25C/29C/19C/10/31E/32E/33C/34C/37E/38C/41CX/71B/28S/19BII/
12C/15C/32SII/33S/35S/48GX/50G/Prime/DM32/DM42]
[TI: 50/50A/51A/55/52/56/57/58/58C/59/60/66]