There are five recipients of the EK2 listed, but none containe Gustav in their names:
Theodor Marten (Gren. R. 9)
August Friedrich Ferdinand Marten (Inf. R. 49)
Peter Eduard Marten (Feld Lazareth d. VII. AK)
Hermann Julius Marten (Inf. R. 48)
Johannes Ludwig Marten (Inf. R. 84)
Do you have any addtional information that might help narrow them down?
As for the list, a good friend of mine discovered it in an archive in Germany and was kind enough to provide me a copy of it. The list itself was published by the Prussians in 1877, and is a gold mine of information, as it provides first names, something the Prussian official sources almost never did!