Just picked up a cool old panel today. It's a 41 cell Arco panel. Strange that it is glass with laminated cells and an aluminum box behind the laminate with about 5/8" open air space. In full sun I got 22.86. Voc. and .995 Isc. I believe from the model number it is an 18 watt module. Another relic to add to the collection.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.