The serial number is from early in that run, so it was probably made in 1954. It is marked "Hard Rubber" on the shank. These are considered to be among the best hard rubber mouthpieces ever produced. Not only are they finely crafted, but the rubber compound is extremely resonant.
Hard rubber Brilharts can be divided into two generations, this being a late one, with flat side walls, similar to the standard Ebolin and Tonalin variants. It is stamped 3 on top. Don't let the low number dissuade you though.The actual tip opening measurement is. 070, which is the perfect spot for many contemporary players. For reference, that is just a hair smaller than a modern Meyer #5. This mouthpiece is in excellent condition. The tip, table, and rails are perfectly smooth. There is some very minor tooth wear on the beak, but nothing that would warrant repair. If you use a mouthpiece cushion over it, you'll never notice it. It is not the original box for this mouthpiece though.
It has a different serial number on it. It is in good condition. The item "VINTAGE BRILHART HARD RUBBER ALTO SAXOPHONE MOUTHPIECE CARLSBAD CA. 070 TIP" is in sale since Thursday, March 25, 2021. This item is in the category "Musical Instruments & Gear\Wind & Woodwind\Parts & Accessories\Mouthpieces".
The seller is "greatlakeswinds" and is located in Milwaukee, Wisconsin. This item can be shipped worldwide.