Don't jump to try and sticky this yet, wait till i'm finished with my work! That said, anyone here with early examples of Maxell tape, do please post info and pics. I'm interested in the front/back of the box, info cards inside, reel type, any date info and leader color/patterns. Some of these early Maxell's will say Hitachi/Maxell on them.
On the topic of used yard sale tapes, ehhhh, not really. It depends on your expectations. Since you said you want the highest quality, i'd say pass. Old tape is exactly that. Unless the seller can give you a history of how it was stored and what machine he played it on, you could be getting anything. Being it is a yard sale tape, it has probably spent the last 20 years stored in the attic or garage. And while it may still sound good playing, it won't offer the highest recording reliability anymore. Dropouts could be numerous for instance. But if you are interested in some tape to just play around with, then sure, go for it. For Scotch tapes 203, 206, 207 and 250 are well regarded. I also believe 150 is seen as a good tape, but i can't remember right now. I have some 175 and it has given me no issues, but for others it has. 111 was also considered to be a good tape in it's time, but much of it was made on acetate and is fragile today. I'd pass on it.
The ONLY Ampex labeled tapes that one should consider buying is 631 and 641. All the rest is pretty much unusable today. Especially AVOID 406, 407, 456 & 457. See the sticky on Sticky Shed at the forum's top. It lists pretty much all of the known offending tapes from all makers. Now if you find some cheap tapes on metal reels, i'd say buy them just for the reels. Especially if 10.5". If not bent, scratched or otherwise damaged, they are great for loading new pancakes of tape onto, or resale.
All i can say about examining them is pretty limited to my own standards. I look for the obvious stuff like mold, breaks, twists and dust. I also look at the tape pack, is it nice and even, or all over the place? A few uneven areas can be expected if the pack has shifted. But that usually moves whole sections of tape, not individual layers. I also like to spool out about a foot or so of tape and have a look at the magnetic surface. If you can see lots of heavy lines, it's been played MANY times, or run on a rough transport. Faint lines can be ok. Also look for water stains on the box, or any other stains for that matter.
Spaceman,
The UD box with the textured gold surface is an older version of the series. Dates to around 1973-75. The oldest gold UDs don't say 35-90, but instead 35-7.
I have done some research on the TDK tape series, but they don't have as big a following, so info is limited. It doesn't help that TDK got out of the reel tape biz years before Maxell did. Audua was their top tape line in the mid to late 70s. Pretty good stuff and should stack up nicely to UD and UDXL. I'd keep it! Best as i've been able to find, the line up is as follows...
S and SD were the basic types in the early 70s. Then SD was replaced with Audua. It came in non-backcoated and backcoated. Then around 1981 The S and Audua series were dropped and replaced with LX and GX. So anyone here with TDK GX reels, you have the top of their line! TDK also made some EE tape and it was labeled as SA. (Just like their TY2 cassettes.)
Anyone with reels of TDK tape also feel free to post info on them.
Oh, it's a UD 35-90, in the gold & black box, & the gold cardboard is textured, kinda classy-looking. 
Do you know much about the TDK tapes? I have a couple Audua ones, L-1800 & LB-1800 (LB is backed), & wondered how they stack up. :scratch2:
