The Supra model has remained pretty true to its roots since its introduction in around 1963. The "Ludalloy" (aluminum) shell has been a constant as has been the overall design of that shell (called the "acoustiperfect" shell featuring seamless spun forming and a shallow and very gradual snare bed). Certain details have evolved through the decades, the badges and throw offs, dropping the internal muffler in the early 80's. The very earliest examples had different snare beds (crimped in) and brass hoops but once things were finalized the overall design and construction has remained fairly constant since the mid 1960's.
Aluminum and chrome plating are somewhat at odds with one another on a chemical level and it is not an ideal combination. Some drums will flake severely while others will remain nearly perfect. There doesn't seem to be a particular pattern to this and theories abound as to why. Obviously the environment that the drum was kept in plays a part but perhaps there were other factors in play as well. Maybe different plating methods were tried or different plating companies were contracted to do the work with some using superior methods, maybe it had to do with the humidity on the day the drum was plated. No one seems to know for sure but newer drums do seem to hold up better, but whether that is due to a something they do differently now or just because those drums are "younger" I don't know. Bottom line though is even the ugliest flakiest Supras sound every bit as good as the ones with the chrome intact so they can sometimes be a real bargain if you are only concerned with the sonic properties of this snare and not so much about appearances.
Supras are very common so there isn't much reason to pay a premium price for a regular model. The 6.5" depth model will generally cost you more, they are less common and have the Bonham connection that boosts the price although they certainly are not a "rare" drum.
The older COB drums that go for big money aren't technically Supraphonics. They are the Super Ludwig model snare which the Supra replaced. Outwardly they are very similar (nearly identical) in appearance but there are a number of differences, most notably the brass shell (which chrome adores and doesn't flake off). They are great snare drums in their own right and probably worth the going rate but they aren't really Supras. There were some brass shelled Supras made at some point in the late 60's and/or early 70's. Those are quite rare though and don't pop up very often. Possibly special drums made for endorsers.
Beginning in the late 70's Ludwig began producing variations on the Supra theme, the first being the brass Black Beauty model. I'm not sure if technically these are considered to be Supra Models but they share an identical design with only the shell material and plating being different. Since then Ludwig has made Supra like models in Brass, Bronze, titanium, and Copper so there are options in the newer drums.
The newest models have rubber gaskets under the lugs but otherwise still look remarkably similar to their 50 year old ancestors.
Two other Ludwig models use the same shell as the Supra, The Acrolite model has the same shell but unplated and with just eight lugs (on the 5" model). This is a snare drum that everyone should own at least one of, particularly since they tend to sell for very little (although prices seem to be climbing as their reputation spreads). The other is the Super Sensitive which is a Supra shell with a much more intricate throw off mechanism. Sometimes these will sell for less than a Supra of similar vintage because fewer people are looking for them, even though it was originally a higher end and more expensive model.
As easy as Supras are to find and as good as they can sound there's no reason not to snag one and give it a try. There is a reason they've remained such a success through over 5 decades.
Anyway, I hope that helps.
