We don't know much about these...
Thomas Caspar, who collects such tokens says:
"Because the Postal Telegraph was the internal USA telegraph arm of the Commercial Cable Company, this is then a U.S. token rather than a British issued token. I assume the phrase "Postal Telegraph" was not used in Great Britain. I guess we can attribute this token to New York, NY because the U.S. headquarters were located there.
I guess the only mystery is what the letters "SRSM" mean and how this token was used."
Bill Burns suggests the following:
"There's some thought among a group of telegraph collectors here that it might be a token for a free message:
'One Standard Rate Single Message'"