Rare MXR phase 90 help!

[RR1417]

Hey guys, I've been setting up a new rig for awhile now and decided to go with a bud box MXR so I did some searching and found this on ebay for 300 bucks, the seller has this as the description:
"Pot code reads 1377717 which places the date of manufacturing to the 17th week of 1977.
The circuit is exactly the same as a 1974 Script Logo phase 90.
This is an EXTREMELY RARE pedal, not many of these were made. Not only is it possibly one of the rarest pedals ever made it is also one of the best Phase 90's I've ever heard. Sounds as good if not better than the Bud Box phase 90's I have owned."
I have not been able to find ANY info on any sort of special edition or a promo, anything, it' was obviously put out in the block script transition phase, if anyone know's anything I'm really interested to find out, thanks. the images are still on ebay: http://www.ebay.com/itm/330809376070?ss ... 1497.l2649