Nice vacuum! I wish mine was that nice!
I just used my Silverado Deluxe today to clean out my car after a beach trip! I got it for free on Ebay as a bonus with an Ultralux Classic (that I've, regrettably, since sold). The Silverado was (and still is) rusty, scratched, dented, faded, and has odd duct-tape residue... but she still runs like a champ, even the cord winder works!
Mine came with the same PN... I'm pretty sure I'm accurate on this: I think the Diamond Jubilee first came with a Light Sand Beige PN with a red reset switch for several years and then switched to a Jade (basically black) PN, like the final Silverados had, but with an on/off switch on the base.
If your Silverado is a Deluxe and has a Diamond Jubilee-style PN that has a red reset switch but NOT an on/off base switch like the later Jade-colored DJ PN, it's very likely still original equipment. I don't think the DJ was ever sold with a black PN with a red reset switch.
I'm not sure I entirely agree that the Silverado was the last of the best Electrolux vacs. My Diamond Jubilee was an '85 model that went from my grandparents, to my parents, to me. In the middle, it was borrowed by my sister and me to clean our college apartments every few months. It *did* need a motor replacement, but not until like 2015ish. That's pretty good mileage, I think. My mom vacuumed several times a week because we had a dog, and the vac was definitely abused when my sister and I were in college. I think that era was still a good era. I miss the metal body vacs and hope Aerus doesn't kill the Legacy and Classic anytime soon. I dig the retro vibe.