The full quote from that text is:
This coin is closely linked in its style and control marks to the Arachosian issue of Sarpedanes represented in the British Museum (ibid no. 1100) and appears to fall like that coin between the issue of Orthagnes/Gadana and Pakores in the same series.
If I remove all the extra information that is not necessary to the sentence, it becomes:
This coin is closely linked to the Arachosian issue of Sarpedanes and appears to fall between the issue of Orthagnes/Gadana and Pakores in the same series.
I'm not familiar with technical classifications of coins, so I'm not sure if it is talking about periods of time, or classifications of series. Here are the definitions that would fit, from Merriam-Webster: Fall (Intransitive Verb):
7 a : to occur at a certain time
her birthday falls on a Monday this year
8 : to come within the limits, scope, or jurisdiction of something
this word falls into the class of verbs
So to "fall between A and B" would be to either occur between time A and time B, or classified between class A and class B.
The text is comparing two coins and saying that they both "fall" (were issued or are classified) between (A) Orthagnes/Gadana and (B) Pakores.