I apologise if someone else has already posted this but I've just checked Scott Bowden's "Napoleon's Grande Armee 1813" to see if 7th (Vistula) Lancers is mentioned as coming to the army from Spain in 1813 but couldn't find it. However looking on his orbats for the Army of the Elbe on 25th April 1813 he does have 3 Officers and 25 Men of the Regiment in 1st Light Cavalry Brigade, 1st Light Cavalry Division, I Reserve Cavalry Corps. This army was of course the survivors of Russia.
How would these 3 Officers and 25 Men compare to the survival rates for other units ? And would they indicate a unit being more than the 100 Lancers that we've had from the various sorces as being the 11th Company of the Guard's Polish Lancers ?