I haven't damaged any of my posters (yet). But I do have a non-poster story from over 20 years ago, when I was about 10 years old (oh well, I just gave away my age).
I collected stamps as a youngster. When I would stay with my grandma in Kansas City during the summer, we would go to garage sales almost every weekend. Oh, how I am nostalgic for those glorious pre-ebay days of garage sale-ing. There were treasures to be found for 50 cents or a dollar, and everybody wasn't yet pricing all their old crap as if it was made of solid gold.
One day, probably in 1995, we went to a sale where someone was offering postage stamps from a medium-sized box for 50 cents per "bag" (a ziploc bag you could fill yourself). I offered to buy the whole box for $3, and the seller accepted.
These were mostly US stamps from the 1920s-40s. But as I sorted through them there were a smattering of nice older stamps too, including some from the
1893 Columbian Issue, as well as some older definitive stamps.
As I continued to sort, a stamp caught my eye. The stamp was obviously old, and I noticed that it said "Saint Louis" rather than "United States Postage" or similar. Even at my young age, I had read enough to be aware of
US Postmasters' Provisional Stamps. These were stamps issued by local postmasters for a couple years prior to the issue of national postage stamps in the USA.
Sure enough, I was looking at a 5 cent
St. Louis Bear. I sensed that this was rare and special, and had an idea it might be valuable. And I was always very careful with my stamps. I delicately maneuvered my stamp tongs to lift the stamp from the pile...and seemingly as soon as the tongs touched the stamp, the paper was so brittle that it cracked and crumbled to pieces.
What was a young boy to do except cry? As far as value, as I recall from my catalog at the time even 20 years ago this stamp was valued in the thousands of dollars. Today, a similar specimen would probably realize at least $5000. And depending on condition these Bears can go for far more.
But at least today I have my Mexican posters to keep me happy. Maybe I have an attraction to brittle crumbling paper.