Actually, Skolot, personal names were left off of the majority of
Parthian coins of all
denominations, which is what can make
attribution so challenging and which is why, for example,
Sellwood and
Assar assign your left coin to different rulers.
"...I have read about
parthian coins at
parthia.com, there is a list of legends that include the rulers name."
The legends page of
Parthia.com includes the coins' inscriptions, but most of these simply refer to the
king as "Arsakes." This was a title, named after the dynasty's founder.
There are exceptions to the general rule, however. Some drachms issued by Vonones I and Gotarzes II, as well as tetradrachms issued by Vologases II, III, IV, V, and VI, all listed the kings' names. I touch upon this issue in the "Basic Iconography" section here:
https://www.forumancientcoins.com/numiswiki/view.asp?key=Parthian%20Coins