On the following page’s item list (which I believe is based on item data received from you):
http://www.zimlab.com/ou...orted-by-name-v-2-2.pdf
Item #169 - ‘Secret Room 1-11’, a miscellaneous item that provides insight into the location of all secret rooms between floors 1-11, similar to a Gem of Finding.
Additionally, I’m trying to determine if Mythril Mail is indeed flagged as a Secret Room item, as I actually found and bought it in Grundig’s store rather than on a floor. I would assume that items purchasable in the store would not be unique, but I’m not positive, so thought I’d ask.