The first time Reese met Finch, he thought he was a Fuchsbau; the impeccably-dressed, bespectacled man was just as sneaky and clever as any of the fox-kin Reese had encountered over the years. Preferring to remain hidden, behind the scenes as it were; these were inherent characteristics of a Fuchsbau.
On the other hand, Finch showed far more self-control than most Fuchsbau, or most Wesen, for that matter. "I'm a very private person," the strange man said many times. Private enough, and controlled enough, to hide his woge, even in times of great stress, which would bring it out of all but the most disciplined Wesen.
(Particularly Fusco, who had been almost ridiculously easy to spot in the group of HR conspirators; he'd been the only Wesen amongst them at the time, and had woged almost instantly. Privately, it still embarrassed Reese that Fusco had caught him off-guard that first time; he was deceptively good at what he did, fitting for the pudgy fox-kin.)
An ordinary Wesen might peg Finch for a Mauzhertz, a tremendously shy and timid creature. But, despite his surface appearance and demeanor, Finch was not at all timid, nor did he lack for courage when the situation called for it. Reese had seen a profound steel in Finch's heart that would be completely out of place in a Mauzhertz, such as the time when Finch, despite great personal risk, drove to the rescue after Reese had been shot by Agent Snow's partner on the roof of the parking garage.
Finch was far too solitary for the gregarious and communal Eisbiber, either, who lived and died by their Lodge.
A less obvious thought was that he was a Hexenbiest (Zauberbiest, actually, but few people were that picky); they were smart and devious, but very concerned with personal appearance, especially given the frankly horrific nature of their true form. But, as one of Finch's favorite authors put it, he didn't "look fair, but feel foul." Hexenbiester usually repelled most people, even if they weren't able to put a finger on the reason. Finch had an aura of mystery to him, it was true, but that was it.
In fact, Finch was so secretive that Reese began to re-evaluate his assessment of him. Maybe he was a Wesen of a rarer breed, with good reason to hid his woge beyond the simple desire for privacy. Perhaps one of the intelligent, elusive Genio Innocuo?
Then Finch was kidnapped by the hacker Root, who had been masquerading as a victim to lure out her intended target. It had taken all of Reese's skill and training, plus help from the totally human but remarkably insightful Detective Carter (and even some assistance from Fusco), to rescue Finch before it was too late.
It was there, at the train station, as Reese gently carried the still drugged but incredibly relieved Finch half slung over his shoulder, that he finally saw the man's woge, and he instantly understood.
In place of mousy brown hair, his head was crowned with brilliant golden feathers, barred in a rich bronze; his glasses perched on an almost delicately formed beak. It was a stunning, even glorious, transformation for such an unassuming man. And Reese knew exactly why Finch had kept it hidden so relentlessly.
Reese had gone his whole life without having even met someone who met a Seltenvogel; most thought them extinct. But if anyone knew that there was a Seltenvogel in New York, Finch would never be safe. Grimms and Wesen and Verrat would die to get their hands on a Seltenvogel's golden "egg", a trophy beyond price.
It all made sense; the avian pseudonyms, the unbending need for privacy, even his birdlike stare.
"Finch," Reese murmured, leaning close to this strange man who had somehow grown into his friend. "Your feathers are showing."
Instantly, the feathers vanished as if they had never been anything more than a figment of Reese's imagination. Finch awkwardly twisted his shoulders so he could look up at Reese, his eyes pleading.
"Please," Finch whispered. Never tell, he left unsaid. Reese had just gained a great deal of power over him, in learning his secret.
Reese's lips twitched in a smile as he gently helped Finch into the waiting car. "I can keep a secret, Harold. You know that. And you're a very private person."