These are vintage blades - made in a time when blades were blades and cartridges were just a figment of King Gillette's grandson's imagination.
Specifically, these are vintage stainless steel blades made in the early 1970- mid 1980s after Wilkinson Sword patented them, and made blades which lasted a lot longer than their carbon steel counterparts. Soon copied by their competitors, there was a bit of a competition (so it seems) as to who could make the longest lasting blades.
As far as which vintage blades I buy - it all depends on reviews of the quality of the blades that you can find online, and what is available at a reasonable cost + postage from places like Ebay.
I've got a rough list of the blades I have
here.
The reason I have more vintage Gillettes than any others is simple - they are the ones that were most abundant, and at a reasonable price when I was collecting.
Vintage Personnas are great (the Personna '74 is up there amongst the best ever) but 5 packs of them go for $30 on the bay.
Schick Plus platinum are also another really good vintage blade, but I missed the time when they were available fairly cheaply because the first two blades I tried were duds and I dismissed them totally until it was too late.
Wilkinson sword blades can be hit or miss. Some of them, like the Light Brigades are up there with the Personna '74s vying for best blade ever, others are nowhere near so good, and it can be difficult to tell by name or packaging which you are getting.
I don't use modern blades at all - the only ones I own are a 5 pack of Derby blades that
someone here decided to send me as a joke. I have enough vintage blades to last until I am in my late 80s!
Vintage blades are getting harder to find, especially for a reasonable price but as most of the ones sold on Ebay come from the US, you should be able to try a few for a reasonable cost.