Price (new): $69.95 (1967)
Cell type: CdS
Measure type: Combination Reflecting/Averaging and 3D Incident. Spot, enlarging, other attachments
Battery: two PX13s or one PX14
Modern Photography Review: July 1961
This originally came out as the Lunasix in 1961, but Gossen eventually redressed and rebadged it in the USA as the Luna Pro. It sold (with various tweaks and alterations) until it was replaced by the sbc model in the late 70s. Quite a long run for a meter.
This was one of the first CdS meters to hit the market and it made a huge splash. Modern Photography's review said it was the most accurate across the scale, and it was great in low-light--two big drawbacks for selenium cell meters. The fact that it took batteries wasn't seen as a big deal.
I wasn't a big fan of Gossen's selenium meters, but the more I see of their later designs, the more impressed I am. This one has a big, easy to read face and calculator dial. I didn't need to read the manual to figure it out. It's not beautifully styled, but it's clean and easy and it works really well. It looks like the design engineers really honed and refined it. It looks like it was made by people who actually use meters, rather than marketing people who are only interested in selling them.
The big drawback to this is that it takes the dreaded mercury batteries, which are no longer sold. Gossen does sell an adapter kit, which appears to be two modern SR44 batteries and a size adapter which also supposedly steps down the voltage to the proper level. I haven't tried it yet. If it works, it seems to me that it would also work in other two-cell meters like the Minolta View-Meter 9 and the Weston Ranger 9. If so, it's a relatively inexpensive ($40) fix.
Gossen revised it in 1966; in the USA they kept the Luna-Pro name, elsewhere it became the Lunasix 3 (there is no Lunasix 2 of which I'm aware). I believe the main difference is that the later version took attachments (see advertisement).
The Lunasix 3 was a gift from Jaap Besterveld in Ireland. Thank you!