Czechoslovakia Doplatne 1928

I have come to the conclusion that these are Czech 1928 stamps but I can find little to no info on any stamps that are Doplatne. I cant find a worth on these stamps (I am assuming not much but still want to know)



Then these last 2 I cant find the worth on the stamp with the 2 perf sides (not sure if it is a different year) and also I have found the second stamp in this picture but not with the Doplatit overprint...please help.

Look in the BOB section of your catalog

They are postage dues, very common and basically worthless. They turn up in various mixtures and lots regularly.

thank you guys!

I agree they are very common and therefore minimum catalogue value but here is a point; the green ones (and also any violet ones you may have OP) come in two perforations - 12.5 (from 1954/1955 printing) and 11.5 (from later 1963 printing). There is even some variation from these numbers.
Although very common, I for one do not yet have a complete set of both perforations. Like so many "common" stamps, they are (i) still sometimes difficult to find and (ii) there is often something interesting about them.

thank you Conker! I will look more closely, although I am still not good with determining the perf.