In reading the novel "La Sentimulo" (found online) I encountered the word "rekonilo", which I would translate as "thing to make something recognized" - possibly like an identity card? In the context of the story, it is an item given to the protagonist to prove his identity to an unknown person. One online dictionary says it means "landmark"; another said it means "recognition tool" - a totally logical translation, but awkward English, and I am unclear what the actual object in the book was - a note? Can anyone help clarify this?
La Sentimulo is a greatly abridged retelling by Roger Imbert of The Bravo (1831), a novel by James Fenimore Cooper. It uses only the 450 root-words of the Zagreba Metodo and about a hundred extra which are included in a glossary.
The passage you are referring to comes halfway through Chapter 2:
„Prenu tiun ĉi leteron. Sub la Ponto de Sopiroj vi trovos Jacopon. Transdonu la leteron al li. Se li petos rekonilon, transdonu al li ankaŭ tion ĉi."
Kaj Don Camillo transdonis iun rekonilon al Gino.
The word comes up again at the end of Chapter 3. A rekonilo is a tool, instrument or object which enables recognition. (The Wikipedia article uses it to mean an emblematic landmark for tourists, or emblema vidindaĵo.) In this context it can only mean a token.
"Take this letter. Beneath the Bridge of Sighs you will find Jacopo. Hand the letter over to him. If he asks for a token, hand over this also."
And Don Camillo handed to Gino some sort of token.
Here is the original version:
"Take this packet," he continued, placing a sealed letter of more than usual size into the hand of the gondolier, and drawing from his finger a signet ring, "with this token of thy authority. Within that arch of the Doge's palace, which leads to the canal of San Marco, beneath the Bridge of Sighs, thou wilt find Jacopo. Give him the packet; and should he demand it, withhold not the ring. Wait his bidding, and return with the answer."
A signet ring is a ring with an engraving on it which can be pressed onto sealing wax so as to imprint a design which authenticates a document at the moment it is sealed.
To seal a document is sigeli, and a seal is a sigelo, applied with a sigelilo onto wax, sigelvakso. The Esperanto word for "signet ring" is sigelringo. The translator used the rare word rekonilo merely in order to avoid adding two extra words to the glossary.
Your understanding of "rekonilo" is right on. From the context you give, it sounds like something other than a note, which would be simply "noto". It's probably a unique object, something that couldn't be easily forged or copied. In English, I might translate it as "token" or maybe "sigil" if there were mystical powers involved.