I believe the differences are:

• 1305s from 2017-18 had exhibition caseback and a blue hand on sub-seconds, but only white text on the dial. Was updated sometime through 2019.
• Alternative strap and box supplied

 

Thank you very much for your answer. According to this, the 1305s from around 2019 with steel case backs and blue lettering on the dial are more or less identical in construction to the current 2305s.

Panerai may have changed only the model number from 1305 to 2305 after selling out the 1,000 or 1,500 pieces (I don't know the number of the limitation at the moment).

 

Panerai changed the reference numbers on all of their watches that came originally equipped with Sportech or other PVC based straps. So many of the watches in this years release that now have a "2" instead of a "1" are simply changes in the straps, the watches remain largely the same.

Long story short: the watch is the same, the straps are different.

This was a confusing switchover for us (I used to work at a Panerai Boutique).