Well, zeroed the meter, put a fresh battery in, and gave the Luna a go. Compared it against the three 35mm SLR's I have that have built in meters (Pentax MX, MeSuper, and Canon AE-1) and it tended to not come within a couple of stops of any of them using reflected metering in any setting that had decent contrast. Am I assuming correctly that the Gossen is metering a larger area, thus a larger "average", than the center weighted meters of the SLR's? If I'm up very close, say within a couple of feet of a uniformly lit surface the Gossen was more likely to come close or match the SLR's. One thing that was curious is that it matched an old Nikon D40 dslr set on matrix metering and the same iso every time without fail. Although I've never used a handheld meter before I'm assuming that with reflected readings I will have to adjust my exposure mentally to try and capture what I want since the Gossen reads such a wide area. Incident readings may work fairly well in my location since it's flat, no trees, and the sun tends to hit everything the same way. Any suggestions or advice you may want to provide will be gratefully accepted.
If you are measuring with the Gossen in reflected mode, comparing to a weighted metering from a camera, be very careful that the metered "target" is evenly illuminated and a consistent texture/color. From what you have described, I think your new Gossen is spot-on accurate, and the measurements from your DSLR I believe confirm that.
I have owned and used Gossens for years, and my personal preference (90+% of the time) is to use them in incident mode. The times I use it in reflected is with the spot attachment, with greater certainty of the area captured. Just my preference..........
It is hard to debate the quality of an incident reading, one argument might be that "I can't get in front of the subject to take a reading", but I would counter with the fact that if I move within some part of a 360 deg. circle I will find a pretty accurate substitute. Stage lighting, and situations like that are different, but in an area with pretty broad luminance incident metering is a great start. Do get the APUG article on incident metering, it is a worthwhile read.
Over the weekend, go outside and take some readings with the Gossen in both modes, you will learn a lot through usage.
Enjoy!
FL Guy
Edit: The Incident metering piece
(there was a url link here which no longer exists)