Cancellation Error?

Would this be considered a cancellation error? I would think that it should have a date in the cancel.

Not an error. It's what's known as a "mute" cancel, typically applied to bulk rate business mailings. Without a date, though, it would be impossible to tell the date of mailing and/or if the embossed envelope value of 2 cents was appropriate.

Of course, it could also not have been intended for this cancel but mistakenly put in a pile that was inadvertently cancelled by this machine.

It either case, it does not really make the machine cancel any more or less valuable. Merely a curiosity at best.

No date means it's third class postage.