Cased First Class Iron Cross

[Skylinechili]

Maked D.R.G.M + KM st ? 

Proof mark 900

[Fritz]

This one is convex in shape, very unusual pin system, never seen one like this before, very nice presentation case.
The 900 mark is 900 silver (90% pure), the cross did not strike me as being silver, it looked more like silver alloy,
but the stamp should confirm the silver content. The core looks like iron, you can check this with a small magnet.
An usual type of iron cross, more a commercial make. The D.R.G.M. is a registered pattern: Deutsches Reichs- Gebrauchsmuster,
this undoubtedly refers to the pattern of the patent pin system. I don't know offhand what KM ST stands for, but I will try to find out.

Here is a non-commercial info site about all German decorations, German States, Empire, Third Reich sections; here you can find the Prussian decorations, German text, but easy to get through, also price guides, which are a bit outdated:

https://www.ehrenzeichen-orden.de/c/deutsche-staaten/preussen-koenigreich

Found: A link dealing specially with EK1, KM ST:

https://www.ehrenzeichen-orden.de/erster-weltkrieg/eisernes-kreuz-1-klasse-1914-mit-nadelsicherung-kmst.html

Significance of KM ST not known, thought to be Königliche Münze, Stuttart, but unlikely. Probably a privately ordered second piece made by various firms and jewellers, research has not revealed much so far. Iron Crosses were awarded up till about 1924, when the chapter was finally closed. "Seconds" or spares were made even during WW2 if required.

[Skylinechili]

Fritz, yes the pin system is what threw me off. Out of maybe 50 crosses I have, this was the only of this type pin. I'll do more research and see if I can't get the maker. 

[Gildwiller1918]

Very nice cross, I have not seen that pin system before either. Please post more information if you get anything.

[Skylinechili]

Found a few other examples. From what I've read they are not common and everything points to Königliche Münze, Stuttgart. They are sometimes referred to as a"Mousetrap"EK1. Also, I misread the hallmark. Closer examination shows 800. 

[Fritz]

The Königliche Münze in Stuttgart was responsable for minting currency, silver, gold, and also silver, gold and bronze decorations for the state of Württemberg. The Iron Cross was not a Württemberg decoration, so this seems unlikely.