Express Mail Corporate Account Labels

As virtually everything post office related is collectible to someone, I wonder if anyone would care to comment on these labels. If my understanding is correct, they can still be obtained from the USPS (through the Postal Store, anyway), if you're a corporate customer.

The current design (per Postal Store website) shows a more modernized eagle logo and the term "United States Postal Service" while still calling it Label 108 with a date of May 2000.

I came across this one recently. It's of older design. It's still identified as Label 108 but with a date of April 1990, using an older style eagle logo and no "United States Postal Service" text.

Is there some reference as to how many varieties of these labels exist or are they just being ignored by collectors as an item of no interest? Are they considered a cinderella?

There are people who collect them. I recently sold an unused Express mail notification card online that dated to the 1990's. I've also sold old blank registered mail receipts so some folks are collecting them. I know of others who collect German COD labels (little triangles), air mail labels (etiquettes) and custom forms. I don't know if anyone has put out any publications yet, but check the APS library. Because they serve as postal function for labeling and/or directing mail I don't believe they really fit into the Cinderella category like Xmas seals.

Hah! nothing, repeat nothing is ignored by collectors.
That's why you NEVER throw anything out.

I know a collector who collected a particular slogan cancel
to evidence wearing on the slogan impression molding,
which gave rise to missing detail.

I collect labels as you describe, which can be broken down
into sub headings, the main branches are:

Postal Labels: Accountable Mail
Postal Labels: Air transport
Postal Labels: Express labels
Postal Labels: Maritime Transport
Postal Labels: Specifying Class of mail.

I would collect that, if I ran into it. I collect USPS tracking labels.