Ausf D and early Ausf A hulls are identical. The only externally visible changes between models occurred in the redesigned turret. The external differences between a Ausf D and a Ausf A have been discussed in several threads on Missing Lynx.
To quote Roy Chow;
"Most older books (before Jentz' Panther: Quest for Combat Supremacy) mistakenly cite the switchover from D to A as the MG port to kugelblende MG mount. As others have said, this is wrong.
Often these older books will caption a photo of an early A (cast cupola, letterbox MG port) as a late D -- these would be wrong.
Books off the top of my head that share this mistake are:
Anderson's "Panther" by Concord
Culver & Feist's "Panther In Detail"
Squadron Signal "Panther in Action"
Sturm & Drang Panther
Hughes and Mann's "Panther tank" a coffee table book"
I would add Spielberger's ; Panther and it's variants, to Roy's list.
Quoting Cran Smith;
"The puzzler is at Panzer Tracts 5-74, as you know, Robert. Jentz makes a general statement about drum cupolas going onto ausf A turrets. However, the single example of this practice that he adduces is a befehlspanzer, judging from the antenna mounts and the plugged coax port. We know about befehlspanthers with zimmerit and drum cupolas. Should we suspect others of being ausf As with new-style turrets (except for the cupolas?) More to the point, we have one example so far of new turret/drum cupola overlap, and it's not a line Panther. It seems pretty safe to argue that for a rule of thumb, drum equals ausf D and cast equals ausf A, until we have more counterexamples."
Quoting Terry Ashley of PMMS:
"The presents [sic] of this new cupola identifies it is an Ausf.A and not a late Ausf.D as some older references would indicate."
There is no mention of cast cupolas being used on the Panther Ausf D in Jentz' Germany's Panther Tank. To quote Jentz from page 57 of GPT; "Among the changes introduced with the first Ausf. A were: The commander's cupola consisting of a cast armor body..."
Again Jentz, Panzer Tracts 5-1; "These photos of Ausf.D produced in August/September 1943 are ample evidence that none were completed with cast commander's cupolas."
In addition, a somewhat higher resolution copy of the above photo in question can be found on page 115 of; Panzer Truppen Vol 2. The square-cut, turret side to turret front welding seam can be more clearly seen, a definitive Ausf A characteristic.