(1) Softer than today's Triangles? Hmm, they could be really old and dried out. Which unfortunately means worthless.
(2) Is the box other than the picture I attached? Cuz that's the only Triangle box I've ever seen in the past 25 years.
(3) You can buy a box of 11, 12, 13, or 14mm Triangles on many websites at this very moment, so the small size doesn't necessarily mean anything.
(4) On the bottom of my box of Triangle tips is a date which I assume is the manufacturing date. Maybe your box has the same. Then again, maybe not, depending on when they started printing the date on the bottom of the box. If no date, maybe there's a manufacturer's code that can be deciphered by someone at Tweeten?
(5) Finally, put all your tips in plastic ziploc baggies to keep them safe from changes in temperature and humidity. If you do business with Joe at Cue Components long enough, you'll have those baggies coming outta your ears! But at least you can put them to good use. (Thanks Joe, I love those baggies!)