Petrified plug wires?

[justa dumb hick]

In my endless, mostly pointless, pondering of all things mechanical beneath that giant dome-light in the sky, I recently stumbled upon an item I cannot fully grasp. Perhaps the more knowledgeable bow-tie connoisseurs among this forum of automotive misfits, could shed light on my quandary.
After many months, years, miles, of minimal maintenance (too lazy) and yet trouble-free dependability, the old C-10 recently expressed a desire for a new water pump. Ordinarily I would have simply waited for the ol' girl to DEMAND a new water pump (Meaning: Bearing squalling like a scalded cat and/or antifreeze mimicking the cow/flat rock scenario). But since it was close to Christmas, and wanting to be on Santa's good list, I figured with only 4 fasteners holding the pump in place I could knock it out in time for beers by the fire and feel good about myself for a change.
Water pump completed, I decided to check the oil... since I cannot recall the last time I pulled a dipstick. As I recached for the dipstick I noticed the plug-wires had lettering on them. Being the avid literary whore that I am, I paused to investigate further. Brushing off the dust, I found something intriguing, and hard to comprehend. So I took a picture and was hoping one of you fine individuals could tell me if these plug wires are indeed from last century... almost 60 years ago? Did GM date code wires? Can this be for real? She runs damn smooth, so I just assumed the ignition components had been replaced somewhere along the way.