David: be careful with the names of these units. The ones on the flags are probably not what you are interested in.
These flags are from the ex-German part of Poland. Initially its army was entirely separate, busy fighting the Germans in the period immediately following WWI. Only later was it integrated into the Polish army. So each unit has two numbers: the one in Wielkopolski army, and another in the Polish Army.
The yellow flag just above has "3PUW" as it was the 3rd Regiments of Ulans in the Wielkopolsk army. But that became the
17th Ulans in the Polish Army. And that is how it will appear in any orbats for the 1920 campaign.
http://pl.wikipedia.org/wiki/17_Pu%C5%82k_U%C5%82an%C3%B3w_WielkopolskichLikewise the 2rd Rifle Regiment earlier became the
56th Infantry Regiment when it entered the Polish Army.
http://pl.wikipedia.org/wiki/56_Pu%C5%82k_Piechoty_WielkopolskiejEdit: added pl.wikipedia.org links. They can be quite useful for checking details.