For a 64.5-65, typically would be no markings stamped into the main body, but originals normally had an ink stamp that identified it. On the nose end that fits into the bellhousing, there will be an engineering number cast into that piece that can help determine if it's correct for your year car. Although, rebuilders mix and match parts, so isn't always a given that everything is right. There are also different end plates.
Another item that is not as easy as it would appear.