It is my strong belief that double-weight prints are worth more. Sales bear this out.
And I don't think Mick signed 1973 of these.
1973 means they printed 1973, I believe. The only known signed edition is through 173 but they have to do a few more- in case of postal damage, loss, etc.
If you look at the Licks lithographs, they are numbered 1/2500, etc but only a few hundred were hand signed.
If there were 2000 of these floating around signed you would see them all over ebay.