Ptolemy II Oktobol Lorber CPE B 234.261-246 B.C. Obv Head of Zeus Ammon r. rv. Eagle standing left head reverted Letter Theta between legs 85.49 grms 45mm The large heavy oktobols are assigned to the reign of Ptolemy III except for this issue. It is probably because none of the smaller denominations of this coinage share the "Theta" mintmark but the earlier drachms with the two eagles does. However since buying this coin in 1990 the attribution of this coin has changed three times first being ascribed to Ptolemy II then later to Ptolemy III and now back to Ptolemy II.
You sort of need to adjust your way of thinking about a chronological series when you approach the subject of the Ptolemaic coins. Arranging them strictly by ruler is not necessarily the best way to understand them. We become so acclimated to using the procession of rulers to arrange and categorize our collections of places like Great Britain, Roman Empire, Seleukid Kingdom, Spain, etc, all of which are made up of series which relate specifically to one ruler or another. Usually they will even bear a portrait of that same ruler. Series like that pretty much self-catalog by ruler and it's natural to arrange them that way. The Ptolemaic coins are not really like that. If you feel comfortable enough with the dating schema of whatever reference(s) you're using - and remembering that the sequence has been established mainly by analysis of hoards and not on the basis of marks identifying or associated with individual rulers - you can sometimes place and/or assign some types to a time frame which falls completely within a specific reign. The issues - particularly the AE's - were not necessarily specific to the rulers and can often span two, or even bridge across multiple reigns. They're really a lot more like US coins in that way. Would you try arranging your US collection by whose administration out of the procession of presidents a specific coin was struck? You can probably easily see how cumbersome and awkward it would be trying to apply that "reign-specific" cataloging to US coins. Ptolemaics are somewhat the same, and you're likely to be a somewhat happier camper in the field of Ptolemaics if you can internalize this principal.
For identification of Ptolemaic bronze coins you may wish to refer to www.ptolemybronze.com and go to the 'coin photos' page which can help pinpoint catalog numbers for hundreds of types. PtolemAE
I highly recommend this resource! - It also contains a link to Svoronos (among many other useful and informative pages.)