The printers code on the bottom flap at rear of Flip back laminated sleeve designates....
7006 TPS Printed and made by Garrod & Lofthouse Ltd. Patent No. 943695 STML 11147 - not certain of the exact patent number.
It would be a fair estimate to state the release date of June 1970, by using the album printers code "7006" = June 1970.
The mention of only the stereo catalogue number on the rear sleeve at the bottom is quite correct, as by the time this sleeve was printed in two pieces, only stereo issues of the album were being pressed, as with other UK Tamla Motown albums, apart from mono compilations.
The original US version of the album was released 06-Mar-70 on Gordy S947, details from track B6 "Friendship Train" completed 30-Jan-70, listed on "Don't Forget The Motor City". - (scroll down page.)