The I./4 was the only unit in Italy to possess Panthers. For the most part this unit was a 'Heerestruppe', an independent unit attached to the Armee. The unit marking was a triangle with the head of a panther, and claw jumping to the left. The marking was only used on the soft-skin vehicles of the unit and not on the Panthers. The I./4 was sent to Italy in Feb 1944 under PzReg 69 to attack the landing at Anzio, remaining in Italy it was renamed I./26 on Feb 16 1945.
The SS-PzAbt 16 was formed in Nov 1943, and was equipped with StuG III. In June it was sent 3 PzBef.IV, and the next month it absorbed the StuG and Marder III of the SS-PzJgAbt 16. In the Fall 1944 the HZA sent a number of Hetzer to the SS-PzAbt 16, but documentation is lacking to confirm if they received them. If they had any they gave them up in Feb '45 to their assigned Armeekorps, and was refitted again with StuG III when they transferred to Hungary.
Markings- The PzJgAbt 16 used the SS runes on their StuG for most of 1943. When the Division returned to Italy in June 1944, the marking on all of the Divison StuGs were marked with Himmler's collar rank (an oak wreath) painted in white on the hull front, and rear. The SS-PzAbt 16 never used the SS runes but did name several of their vehicles, i.e. "Klagenfurt"
Pz Rgt 4 was formed early (1938). The unit served under 2.Panzer Division. For Fall Weiss (pre-Invasion of Poland). I./Pz Rgt 4 was equipped with mostly Pz I & II's. Only a handful of Pz III and IV, with 11 Befehlwagens shared between I and II/Pz Rgt 4 (as of September 1, 1939).
For Operation Zitadelle, 16. Pz Grenadiers Division had 4 Pz II, 32 Pz III (läng 5.0cm), 5 PZ III (mit 7.5 kürz), 11 Pz IV (Läng), and 1 Befehlswagen (As of July 1, 1943).
Info from Jentz PanzerTruppen books
Pz Rgt 4 was with 13.Pz Div from about France on. In 1943, the original I./4 became s Pz Abt 507 and III./4, which was refitting as a Panther Abt, became I/4. The Abt went straight from refit to Italy, without the regiment.
They were one of the first Panther abtn (May 1943) and had ample opportunity to pick up Italian gear after Mussolini fell (it wouldn't be "beute" before then.)
I./4 stayed in Italy until the end of the war. In 2/1945 it was re-designated I./26 and made organic to 26.Pz Div, which had of course been in Italy all along. I./4's original parent div, 13.Pz Div, got Pz Abt 2110 as a Panther abteilung in 11/1944, just in time for Budapest.
I don't know if this abt had a transitory existence as I./4 before redesignation as a FHH unit in 3/45, but I don't think so. And of course, the original I./26 was with GD through 1944, then became I./Pz Rgt Brandenburg and fought with Pz Rgt Kurmark in the Oderbruch. This abt (I./BR) is one of the three candidates for the famous striped late ausf Gs in Jentz and one of the Concord books, along with I./29 and (more plausibly) 5.Pz Abt with 25.PzGr Div.
SS PzGr Div RFSS went to Italy for R&R in early '44, but found itself otherwise occupied there until 1945.
16.SS-PGD. June 1, 1944, four SS-PGD's (4, 16, 17, and 18) were refitted. Each had a SS-Pz Abt of 3 StuG Kns. Each kn. having 14 StuG's.
The I/4.Pz.Rgt. was of 13. Panzer Division, but it was not refitted in Italy. It received 76 Panther in Germany, but before rejoining the 13. PD in the Eastern Front, it was sent via railway near Rome in February 1944, to reinforce the German attacks against the Allied beach-head around Anzio and Nettuno. The story of the Abteilung (battalion) is long and detailed. It had as unofficial sign the head of a panther (someone wrote of a bear) in a triangle, but used only on light vehicles (apart for the Lince armored-liaison car, also on cars), not on the Panthers Ausf. D. A and G in use (the last tanks arrived in November 1944).
The 16. SS PGD RFSS had StuG III Ausf. F/8 (in the Pz.Jg.Abt., sometimes called StuG Abt., it was derived from the same unit used in the RFSS Brigade in Corsica) and StuG III Ausf. G (in the Pz.Abt.). There were no other armored vehicles (even if included in the theoretical organizational chart for a PGD 1943 or 1944), apart for 14 Marder III Ausf. M in a company of the Pz.Jg.Abt.. The most of the AFVs were lost in the hard fighting in Italy in March - July 1944. In the Fall of 1944 remained only some StuG IIIs.