I'm looking at the financial definition of series: a group of stocks or options that have common characteristics. Source
How would I form the possessive and plural of this term? I'm guessing it is series' and series respectively.
Sample sentences, not sure of correctness:
He purchased one series.
He purchased multiple series.
This one series' characteristics are worth researching. <- This feels like it should be series's, but it looks so wrong.
These series' value is unmatched.