John Stassins who runs a couple of coin shows in Connecticut asked me to run a note by the currency collectors who may know more than he does, whether this specially signed note is anything special.
My best guess is that R. Shuster & Co. was a Philadelphia banking house and they were transferring the value of the note to the designee(s) much like signing over a check, and as a way to vouch for its authenticity. Texas became a state in 1845 and the state legislature probably took their time paying off the debts of the Republic. But by 1849 I suspect the legislature wanted to pay off and pull these notes from circulation. To my knowledge the endorsement is not of historic value, but someone else may know more. It's not a signature, per se; it was probably endorsed by a cashier or bank officer. Btw, my interpretation of the script is "...Record C as per act of..." The mystery letter looks very similar to the "C" in Shuster & Co.