Let me preface my post by stating that I am not licensed to practice law in Pennsylvania and that this post should not be taken as legal advice.
That being said, Section 2307 does not apply to shed antler or antlers from deer who were killed legally.
Regarding Section 2312, a couple things jump out. First The rule refers to the purchase (or sale) of 'any game or the edible parts of game or any protected bird or animal or parts of any protected bird or animal'. It also begins with 'unless otherwise provided', which suggests that there are allowable methods to buy or sell these items. I would argue that this rule does not apply to shed antler, since these items are not 'parts of an animal' at the time that they are collected.
The exceptions to this rule allow for the sale of 'the sale or purchase of any inedible part thereof, from game or wildlife lawfully killed, if such parts are disposed of by the original owner within 90 days after the close of the season in which the game or wildlife was taken'. Therefore, if following the letter of the law, you could purchase non-shed antler (from animals that were taken legally) between September 1 and April 10th(ish). However, I doubt that a reasonable person would choose to apply this regulation to non-shed antler (from animals taken legally) no matter what time of year it is.
Further, I don't believe that either of these rules could be applied to the sale of pens made out of legally obtained antler.