I will start a list of common abreviations that we take for granted when talking about many of these pieces. I'm sure "The Evil One" will add to it!
Common Terms
RK = Ritterkreuz (Knight's Cross)
mK = mit Krone (with crown) anglicized as wC, wK
mS = mit Schwerter (with Swords) Often anglicized to wX
X = Schwerter (Swords)
XaR = Swords on Ring (some Orders had this appendage)
1.Kl. = First Class
2.Kl. = Second Class Both of these will often be stated as RK1, RK2, etc.
mKD = mit Kriegsdekoration (Austro-Hungarian on many awards)
Prussia
HOH = Prussian version Hohenzollern House Order (3 class usually, with X or not)
EK = Eisernes Kreuz (Iron Cross) sub-abbreviations: EK1, EK2
EK2w = Iron Cross on the "white-black" noncombatant ribbon
(P)KO = Preussen Kronen Orden (Prussian Crown Order)
(P)RAO = Preussen Roter Adler Orden (Prussian Red Eagle Order)
KDM = Kriegs Denkmünze (War Medal-- must specific which one)
DA = Dienstauszeichnungen (Long Service award, class specified by number which varied for years over time as in 1= 21/15, 2 = 15/12, 3 = always 9 years. Could be medals or brooches and so specified)
LD = Landwehrdienstauszeichnung (1 for XX years 2 for the broocch/medal. Prussian/Reichs is normally assumed, preceded by B for Bavarian, S for Saxon, or W for Württemberg versions: SLD2, WLD1 etc)
® = Lifesaving Medal on Ribbon (identical glyph used in Rank Lists)
VK/PrKHDK = Prussian War Effort Cross (take your pick!!)
GMVK = Gold Military Merit Cross
MEZ = Military Decoration: 1 (silver cross) 2 (silver medal) on both version EK ribbon
PrAEz = General Decoration (usually the silver medal on RAO ribbon)
Baden
BV = Militär Karl Friedrich Verdienst Order (with class number-- 3 = Knight)
BZ = Zähringen Lion Order (number and letter for class-- 3a = Knight 1st, 3b = Knight 2nd Class, 4 = Merit Cross etc)
BsV = Merit Medal in silver often with designation for on the MKFVO ribbon
BKV = War Merit Cross
BK = Cross for Voluntary War Aid
Bavaria
BMMJO = Military Max Josef Order (3 = Knight Class)
BMV = Militär Verdienst Order (Classes 4, 3, O, 2 up etc)
BMVK = Militär Verdienst Kreuz (Classes 1, 2, 3 with or without Crowns and Xs)
BL = Ludwig Cross
BDA = as Prussia, above
BLD = as Prussia, above
with relevant number for class, viz. BMV4X, BMVK3XmKr
Saxony
SH = Militär Saint Heinrich Order (3 = Knight Class)
SA = Albert Order (Classes as SA3aXmKr, SA3bX etc)
SV = Verdienst Order (SV3aX etc)
SFAM = Friedrich August Medaille (S = Silber, B = Bronze so SFAM-S etc)
SKz = Sachsen Ehren Kreuz (Saxon Honor Cross)
SK = War Merit Cross
Württemberg
WM = their Militär Verdienst Orden (3 = Knight)
WF = Friedrichs Orden
as in WF3aX = Knight 1st Class with swords
as in WF3b = Knight 2nd Class (peacetime)
WK = Wüttemberg Krone Orden
WKrz = Wilhelmskreuz (with X or without)
WgM/WsM = Bravery/formerly "military Merit" Medals in gold /silver
WR/®= LifesavingMedal: NON-Wtbg Lists/Wtbg Lists (wherein the Prussian was PRM not ® )
Hanseatic Cities
BH = Bremen Hanseatic Cross
HH = Hamburg Hanseatic Cross
LüH = Lübeck Hanseatic Cross
Hessen-Darmstadt
HP = House Order with class numbers
HT = Hessian Bravery Medal aka General Decoration "for...." (multiple purpose reverses specify: bravery, long service, lifesaving)
HS = Hessian Military Medical Cross
HK = the untranslatable pinback 1917+ "Warrior Decoration in Iron"
Hohenzollern
HE = Princely Honor Cross (house order) all grades with class designations with ot without Xs
Mecklenburg-Schwerin
MG = Griffin Order with class numbers
MMV = Friedrich Franz Cross (1 = 1st Class, 2 = 2nd Class)
Mecklenburg-Strelitz
MStK = Cross for Distinction in War (1= rare 1st class, 2= usual 2nd class)
Oldenburg
OV = House Order with class numbers
OK = Friedrich August Cross (1 or 2 Class, 2a = with "vor dem Feinde Spange) sometimes, God forgive us, we use "OFAK" which was the NAVY abbreviation for this, while the ARMY used "OK."
Brunswick
BrH = House Order with class numbers
BrK = Ernst August crosses (1 class, 2a 2nd with "horse" device, 2 class)
Anhalt
AB = House Order of Albert the Bear with class number
AK = WW1 Friedrich Cross
Lippe-Detmold
LH = -Detmold version of the House Order with class numbers
LKr = WW1 War Merit Cross
Schaumburg-Lippe
SLH = Schaumburg- version of the House Order with class numbers
SLK = Cross for Loyal Service (their "EK" despite the "long service" sounding name)
Saxe-Weimar
GSF = White Falcon Order with class numbers, Xs etc though "SWF" also used and I prefer that
GSWA = General Decoration: 1 gold, 2 silver, 3 bronze with and without Xs (NOT "SWAfrica Medal"!!!!!)
Thüringian "Ernestine" Duchies
EH = Saxe-Ernestine House Order, common to the hyphenated Saxe-Duchies of -Altenburg, -Coburg, and -Meiningen. The actual GERMAN abbreviation was "HSEH" but even we must Draw The Too Obscure Line someplace!!!
SMK = WW1 Saxe-Meiningen War Merit Cross (for officers, the "crowned B" medal )
SMM = WW1 Saxe-Meiningen War Merit Medal (for enlisted men)
AT = WW1 Altenburg Bravery Medal
Reuss
RE/RäE = House Order with distinction in older (RäE) and younger (RjE) lines, class numbers with or w/o Xs
RgM/RsM = medals of above (no "line" distinction) with or w/o Xs
Schwarzburg
SEK = House Order (the "Honor Cross") with class numbers and w or w/o Xs
SKM = Silver War Merit Medal
Waldeck
WV = House Order (the "Honor Cross") with class numbers and with or without Xs
WgVM/WsVM = gold and silver medals to above, dittos
Austria-Hungary
ÖM3K = Military Merit Cross 3rd Class with War Decoration
ÖT = Bravery Medals, with g old, s ilver (1 and 2 classes), b ronze class designated like "ÖbT"
Ö VK = Merit Crosses with class designations, with and without crowns as in ÖgVK, ÖsVKmKr etc
Bulgaria
BT = Bravery Order/Cross with class designations
BA = St. Alexander Order with class designations
BO = Military Merit Order (peace or war had Xs)
Turkey
TH = Turkish War Medal star aka Gallipoli Star aka Iron Half Moon
TL = Liakat Medals (1 = Gold, 2 = silver)
TI = Imtiaz Medals (1 & 2 as above)
TM = Medjidie Order (number for class)
TO = Osmanie Order (number for class)
TR = Lifesaving Medal