Pre-War type Crosses of Merit: 2nd class (Silver) and 3rd class (Bronze).

Reverse of pre-war 2nd and 3rd class showing the cut-outs between the arms and rays.
Some early pre-war issues are numbered (stamped) in the center.  Some exile WW-II crosses made by SPINK will be marked as such near the top.

Pre-war private purchase 1st class cross made by NAGALSKI.  Arms and rays are not separated on this issue.  The image on the right is the marking of the maker on the reverse, A. NAGALSKI, WARSZAWA.  Persons sometimes obtained (at their own expense) duplicates or replacements for lost medals.  These private jeweler's issues are more un-common.

Bronze Cross of Merit with Swords.  This Original example was produced in the workshops of the Second Corps during the Second World War.  It was cast using a sand mould, which gives it a rough appearance.  Spink made examples exhibit higher quality.  The Swords device (especially Swords copied from the Independence Cross) were added to some Pre-War Crosses and were issued during the War, mostly in Poland, to those in the A.K.  The Cross with Swords is a military award for bravery not in direct combat (combat bravery usually earns a Cross of Valour).  Crosses with Swords are still made today and replicas are on the market in fair numbers.

 
Typical communist issue of 1st, 2nd and 3rd class awarded between 1952 and 1989.  The arms and rays do not have cut-outs.  Miniatures (in this case with enamel "ribbons") are a nice addition.
 

Recently produced 1st class cross.  There are no cut-outs on this example, but some recently made crosses do have cut-outs similar to the pre-war type.