The Zork Anthology comes with several game goodies such as maps, manuals, calendars, brochures, and other files.

Besides the manuals, which I assume are authentic Infocom manuals, its hard to tell which of the other goodies are things that were originally included with certain games, which are bonus items never included, and which item corresponds with which game.

I would prefer not to examine these files if they contain spoilers or things never included in the Infocom release.

Without giving spoilers, can someone explain what these goodies are?

GAME GOODIES
------------------
MANUALS 5 MB
THE GREAT UNDERGROUND EMPIRE: A HISTORY 1 MB
THE LORE AND LEGENDS OF QUENDOR 3 MB
MAPS (5) 7 MB
CALENDAR 3 MB
BOZBARLAND FLYER 1 MB
G.U.E. ON NINE ZORKMIDS A DAY 2 MB
GRAYSLOPES BROCHURE 1 MB
FROBOZZCO INTERNATIONAL ANNUAL REPORT 1 MB
SHAREHOLDER LETTER 1 MB
STOCK CERTIFICATE 1 MB
ROCKVILLE ESTATES BLUEPRINT 1 MB
PARCHMENT SCRAP 1 MB

Thank you.

I'm probably coming way too late, but as I've been examining the subject of the extras of the Zork Anthology for a personal project of mine (and this without owning the Zork Anthology on Gog-thank goodness for the existence of Infocom Documentation Project and Museum Of Computer Adventure Game History!) I examined this subject as well.
Here's a breakdown as to which game each extra corresponds:

-2 manuals=The manuals for Beyond Zork and Zork Zero. Both of those are from Infocom Documentation Project.(as this post states) Zork 1 also includes a manual in the install folder and a shortcut created in the Start Menu (as per this post). The manuals for Planetfall, Zork 2 and Zork 3 aren't in the extras but they might be in the install folders.
-The Great Underground Empire: A History=was included along with the Zork 1 manual
-The Lore and Legends of Quendor=was included along with Beyond Zork
-5 maps=Apparently maps for 5 out of the 6 games in the package-the Planetfall map is probably the one missing.
-Calendar=was included with Zork Zero
-Bozbarland flyer=along with Zork 2
-G.U.E. On Nine Zorkmids a Day=along with Zork 2
-Grayslopes brochure=along with Zork 2
-FrobozzCo International Annual Report=content along with Zork 3
-shareholder letter=along with Zork 3
-Stock Certificate=along with Zork 3
-Rockville Estates blueprint=along with Zork Zero
-Parchment Scrap=along with Zork Zero

Thanks, I appreciate the info.