We'll have to dig this out and lit it up again.

No idea about the date code stuff, but this lamp is very interesting. Usually green metal halide lamps (using thallium iodide I believe) don't have the white refractory coatings on the ends of the arc tube, simply due to the fact that thallium iodide doesn't need as high of an operating temperature. Interesting to see that this lamp does indeed have a refractory coating. It is also interesting to see that the wire going to the distal electrode is sheathed, I think this is usually only necessary with lamps containing alkali halides like lithium or sodium. Looks like they just made this like any other MH lamp except with an altered fill just to make it green. Cool example

It was probably easier to standardise production over the whole range, then just alter the fill to get the different colours...

I think it's safe to assume that the lamp was made in September 2009. The factory location is certain though, it's Steinhöring, Germany. As for the presence of white coatings on the burner and the glass sheath on the side wire, this is clearly the result of a standardized production of MH lamps. This approach costs less than changing the lamp design (except for the salt dosage) for their colored variants. While the presence of the burner coatings is not an issue here, the limited of photoelectron emission may be problematic as the formation and accumulation of sodium iodide as a result of impurities can cause the light color to gradually lose its saturation. As opposed to white and other colored quartz MH lamps, the blue and green ones are the only ones which actually benefit from the electrostatic charging of the burner during operation. Some manufacturers even changed the design of their blue and indium-based high-CCT MH lamps to actually increase the rate of photoelectron emission in order to maintain a more stable light color through life.

@Max
More stable light output? How interesting to hear! I never thought of that, but that definitely makes sense for the lamps that rely on not containing any sodium to produce their proper colors.