The Tally Marks Represent Captain Rex's Growth Wrecker says, "Eleven more successful missions. Like there was any doubt," confirming the tallies represent missions, not kills.
Tally marks or tallies were a way of marking a number for several things. During the Clone Wars, several clone troopers bore tally marks on their helmet to signify their kills. Captains CT-7567 "Rex" and CC-5576-39 "Gregor" were some clone officers that possessed tallies, however Rex stated he didn't keep track.
Turns out, they were on Joe Johnston's original Boba Fett armor concepts; and later expanded as “jaig eyes”, a Mandalorian emblem that “represents the eyes of a shriek-hawk”2 and is awarded to Mandalorians- and later Clones- as a mark of honor for acts of great courage.
Both his Phase 1 armor and Phase 2 armor consist of blue striped markings with distinct "Jaig Eyes" painted on his helmet, a range-finder (antenna), pauldron, and a kama with blaster pistol holsters.
Jaig eyes—a simplification of jai'galaar'la sur'haii'se, translating as "shriek-hawk eyes" in Mando'a, and more commonly referred to simply as jaig—were a Mandalorian sigil bestowed by clan leaders as a mark of honor, awarded for particular acts of bravery.
The ONLY BATTLE Captain Rex Was Allowed to Wear His ARC Trooper Armor - Clone Wars
Why is Captain Rex's Phase 2 helmet different?
Rex's helmet, which he wore in the latter half of the war, was a modified combination. of both Phase 1 and Phase 2 clone armor, which we explained in a recent video. As other clones transitioned to standard Phase 2 gear, Rex welded his new and old issued armor. into his own hybrid.
Since Tano no longer held an official position in the Grand Army of the Republic after leaving the Jedi Order, Rex was formally placed in command with Tano serving as a civilian advisor. Despite this, all of the clones, Rex included, deferred to her and painted their helmets in imitation of her facial markings.
Kamas (or belt-capes) were skirt-like armor accoutrements worn from the belt. In the later days of clone trooper Phase I armor, Clone Commanders, Clone Captains, clone commandos of Clone Force 99, and Advanced Recon Commandos added blast-resistant kamas to their kits, along with other gear.
Trivia/Facts. Captain Rex (an Elite Clone Officer) and Captain Fordo (an ARC Trooper or Officer) both used/use DC-17 blaster pistols as their primary weapon. Most officers who used them as their primary weapons would dual wield them.
Rex shed his clone armor for a slaver's garb when he joined Obi-Wan, Anakin and Ahsoka in infiltrating Zygerria in an effort to rescue the enslaved colonists of Kiros. Rex and Obi-Wan were taken captive and treated brutally in slave pits on the planet Kadavo.
A: Captain Rex modified his suit. He did not like the phase 2 clone trooper armor as much so he welded the phase 1 chest piece and the phase 1 T visor to fit his needs. That's why there are orange marks on his helmet and chest.
As a clone trooper, he was cloned on Kamino from bounty hunter Jango Fett and ages at an accelerated rate, aging twenty years in ten years. As Anakin's Clone Captain, he goes on many missions with Anakin and his Padawan Ahsoka Tano, sharing Anakin's quick-thinking skills and recklessness at times.
Each Jedi Master or Knight that has the rank of “General” is given a legion of clones. The blue-striped soldiers of the 501st serving under Anakin, like Captain Rex, wear blue; the orange-striped soldiers of the 212th serving under Obi-Wan, like Cody, wear orange.
Like other clone trooper officers, Rex was given ARC training. After his training was complete, Rex was assigned command of the 501st Legion's Torrent Company.
Commander Wolffe's alternate Phase 1 helmet was originally an "easter egg" hinting the transition to Wolffe's Phase 2 helmet design for Season 4 during the Clone Wars Season 3 finale episode "Padawan Lost". Wolffe often disliked C-3PO and R2-D2, for he was often annoyed with how C-3PO often talked endlessly.
Anyway, in answer to your second question, Rex is not a Mandalorian. His armor bears a resemblance to Mandalorian armor, however, because the clone template Jango Fett wore Mandalorian armor, and the armor of clone troopers was based upon Fett's.
Because otherwise the other clones wouldn't recognise him. It's the markings on his helmet that make him unique from the other clones to show superiority.
