from the left: 239g, 204g, 204g
The left one is the original metal construction one, centre and right ones
are newer plastic construction with slightly different names on bevel,
The right hand one is the newest with CZJ inscription, I guess. Some say
there is "Meyer Optik" version of this Prakticar 28mmF/2.8. Also I saw
the lens with chrome metal or aluminum filter ring on some german site.
Said metal ring one might be the first version with different optical design.
(I saw Meyer-Optik one at eBay 2015-Sep-29 & 2015-Dec-07.)
See > http://zeissikonveb.de/start/objektive/wechselobjektive%201980er/feinoptisches%20werk%20görlitz.html

The letter "P" on the right hand lens indicates "PENTACON made",
however it might have been made by I.O.R. in Romania.