This Twitter user ordered AKIHIDE's Acorn Locket Pendant via Musing and is currently using the photo as his/her profile picture :
https://twitter.com/prussian_laam
Every order of the Acorn Locket Pendant includes an autographed photo card of AKIHIDE with a serial number that he wrote on the top left corner of it
It's a shame that the image of AKIHIDE used on the photo card wasn't included in both versions of Kikai Jikake no Yuenchi -Electric Wonderland- and frankly paying ￥18,000 for both the locket pendant + photo card doesn't sound worth it to me D: