I was wandering around Washington, D.C., recently, not paying attention to where I was, thinking about codes and ciphers, when suddenly it hit me. No, really: a blast of wind blew a paper right into my face. I looked at it and saw the following:


I looked up and determined that I was on Independence Avenue between First and Second Streets, SE. Then I looked down at the paper again and realized it was telling me to go somewhere and use a certain door. Where and what door?

  • $\begingroup$ Now if I only had a table to decode this, B Ac PuTc CrHf no that doesn't work $\endgroup$ – Jasen Jul 20 '19 at 5:51
  • $\begingroup$ I have a different theory about "periodic" but haven't been able to make it work so far. $\endgroup$ – Gareth McCaughan Jul 20 '19 at 17:24
  • $\begingroup$ @GarethMcCaughan just FYI I've just edited the question $\endgroup$ – msh210 Jul 21 '19 at 18:15
  • $\begingroup$ The edit you mention is entirely consistent with my theory about what "periodic" is referring to, but I'm still a few insights short of actually being able to do anything with it. $\endgroup$ – Gareth McCaughan Jul 21 '19 at 22:24

I am wandering around Washington, D.C, paying closely attention to where I am, thinking about this riddle I am trying to solve. But nothing is gonna hit me.

I have a paper in my hands on which I wrote the following

LA Building, Hermes
LAC Bldg A, Hermegs

Can anyone help me to identify this building? I must find and use his door!


Suddenly my phone rings. Its M Oehm. He tells me to go back to the Library. He sounds very excited.

M Oehm: "Perhaps here? The rooms of the building in question have the right letter code."

He found out, that John Adams Building, the name of the LoC building, is abbreviated with LA, maybe LA5 points us to the fifth floor of the library. And even better, Hermes is there.

I hung up and started running back to the library.

At the west entrance from 2nd Street I finally found it. The Hermes-Door.
The first line on my paper was correct: LA Building, Hermes.

For those interested what I wrote on my paper:

Washington, D.C, at Independence Avenue between First and Second Streets, SE is the Library of Congress
The numbers given are valid ISSN Numbers, searchable at the LoC Website.
The found records have a blast of informations, I chose the Library of Congress Call Number

ISSN Number Call Number
0589-9443 LA5.C64
2472-6354 BL1
0391-2302 DG11.A57
2375-7868 HE1
2378-8968 RM1
0733-5229 E839.G37
2314-7539 S1
Now, only taking letters into account that gives
LA5BL1DG11HE1RM1E839S1 -> LABLDGHERMES -> LA Building, Hermes
or with Sub-Item-Number
LAC5C64Bl1DG11A57HE1RM1E839G37S1 -> LACBLDGAHERMEGS -> LAC Bldg A, Hermegs

Note: All entries are classified as periodic or newspaper ("a periodic message")

Maybe this leads to an answer? Maybe I'm stuck wandering around in Washington, D.C.

Finally, there is a happy end.
Thanks to M Oehm for "calling" me, I would never have looked there.

| improve this answer | |
  • $\begingroup$ You're correct! Now you just need to find the building and the door. +1. $\endgroup$ – msh210 Jul 22 '19 at 12:37
  • 2
    $\begingroup$ Perhaps here? The rooms of the building in question have the right letter code. $\endgroup$ – M Oehm Jul 23 '19 at 7:05

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