Looking at your picture, you've got a MM 2475-65 Check out the model chart. http://www.pacair.com/mmamps/Misc__Info/Model_Chart/model_chart.html MM used the 65 watt power rating series in their first generation, which also used the 12Ax7 phase inverter. The 12Ax7 is on the left side in your picture too. Yours also has the original speakers, which are alnico, adding to the legend of your score. IF you decide to swap speakers for something lighter do not trash those speakers.