The old cato-prone C5-3's have a "X" in their date code.
All my old ones either have a "Z" in their date code or were way prior to "X".
I only had 3 with the "X" date code. One of them blew up my original Mars Lander built from a 1970 bagged kit. The other two I mounted to sticks and launched them like bottle-rockets on the 4th of July. One flew fine, the other made a good M80 simulation.

AC Supply now has the C5-3 in stock.
I'm going to order at least 10 packs as they have them for like $7 and a few cents change.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !