Those would be hard to pass up, beautiful. Seeing a nice shiny Balanced Adjustable never gets old.
Based on catalogs and info posted over various threads, here is my interpretation. Corrections on anything I got wrong are always welcome. The only way to 100% confirm a 156 is checking for the 30mm exhaust valve size.
- A 109 is the original and unbalanced version. Produced from 1969 until 1985 and can be fully upgraded to Balanced Adjustable status.
- Catalog #11.150.000 (or .152. if it was sold as octopus) replaced the 109 in 1985. #150 is the original Balanced Adjustable with 26mm exhaust valve. These will have serial number stamped/engraved on the body below the mouthpiece. Depending on when and where they were produced these have several factory combinations of adjustment knobs, bodies, and faceplates. A few of these have the serial number above the mouthpiece in same style as 156.
- Catalog #11.156.000 is is the CE version of the Balanced Adjustable with 30mm exhaust valve. These usually have the serial number etched above the mouthpiece with what looks like dot peen marking. The CE mark is usually stamped/engraved just above the adjustment knob. It was made from about 1995 until 1998 and has a couple variations in body and faceplate.