Yep, disappearing ink. Is what we used. Used to cost us a fortune way back when, but then some little kids came up with a recipe and posted on the internet and only charged us a few hundred $$$ to access it and copy it so we can make our own. Has saved us $Thousands upon $Thousands in purchasing disappearing ink alone, and when you get into what we saved over not having to pay out for blank, and obvious fake receipts unless proved otherwise, we all ended up with vacation homes (mansions) in the Bahamas, France, South America, Tokyo, and you name it. No, just joking.
By the way on a serious note, when I was a kid I worked after school at an auto parts store that was a nationwide chain store. Back then ALL warrantees on things like batteries were "prorated". Meaning every month a certain amount got deducted for usage. Say for instance a person, you, purchased a 5 year battery and paid maybe $80.00 as an example. Say for instance, the amount prorated (deducted) per month for wear and tear usage was $2.00. That means after a year, 12 months, your battery lost $24.00 in value, and was now worth $56.00, not the $80.00 that you paid when you bought it. If it went bad and you brought it in, we would credit you $56.00 or whatever was left after how ever months was prorated, so if a replacement cost $80.00 to replace still, and we credited you $56.00 towards a replacement, that meant to get the replacement would cost you the difference of $24.00. Do that after 2 or maybe 3 years, and by the time prorated really kicked in, a 5 year battery had a worthless warranty. See what I mean? 3 years multiplied by 12 multiplied by $2.00 equals $72.00 in usage and wear and tear, and you ended up with the remaining $8.00 credit towards a warranteed battery. I don't know if they still do that, but back then thats how all of the major battery manufacturers warranties worked, except for whatever the $$$ amount of the "prorated" costs. Now, this was the mid-1970's and back then, the worst warranty as far as batteries went was AC-Delco. For one...back then...their batteries didn't hold up for squat, and they had the largest prorate cost. Seems to me that back then, after prorating, a 5 year battery from then was worthless after less than half of its life or warranty. So that I don't get myself in trouble for disparaging them, I'm certain that they are much, much, much better these days whether they are or not. Grin
Mark