![File:1929 National Triolian (serial number 1081) in guitar case - ResoSummit 2012 (2012-11-09 17.40.01 by brad bechtel).jpg - Wikimedia Commons File:1929 National Triolian (serial number 1081) in guitar case - ResoSummit 2012 (2012-11-09 17.40.01 by brad bechtel).jpg - Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/9/92/1929_National_Triolian_%28serial_number_1081%29_in_guitar_case_-_ResoSummit_2012_%282012-11-09_17.40.01_by_brad_bechtel%29.jpg)
File:1929 National Triolian (serial number 1081) in guitar case - ResoSummit 2012 (2012-11-09 17.40.01 by brad bechtel).jpg - Wikimedia Commons
![National, C-series Roundneck Green Duolian Resonator Guitar, 1934 - Rich Robinson (The Black Crowes) | Tune Your Sound National, C-series Roundneck Green Duolian Resonator Guitar, 1934 - Rich Robinson (The Black Crowes) | Tune Your Sound](https://www.tuneyoursound.com/sites/default/files/dsc07916.jpg)
National, C-series Roundneck Green Duolian Resonator Guitar, 1934 - Rich Robinson (The Black Crowes) | Tune Your Sound
![File:1929 National Triolian (serial number 1081) - ResoSummit 2012 (2012-11-09 17.40.22 by brad bechtel).jpg - Wikimedia Commons File:1929 National Triolian (serial number 1081) - ResoSummit 2012 (2012-11-09 17.40.22 by brad bechtel).jpg - Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/7/7a/1929_National_Triolian_%28serial_number_1081%29_-_ResoSummit_2012_%282012-11-09_17.40.22_by_brad_bechtel%29.jpg)