what is your oldest mon in the bank?

Sort by recent...my oldest mons listed from the bottom up.

Bulbasaur ...my starter
Aerodactyl...caught wild on day1 of my account
Kangaskhan...first hatch. 93% IV Low Kick EQ
Dratini...first one - walked 400km+ so far
DugTrio...Mud Shot legacy
Koffing...Acid Legacy

My charizard july 14 88 ivs with a legacy moveset ember and fireblast

my starter charmander!

A Chansey at Lvl 1(!) with CP 20, hatched 7/30 two days after I started playing.

Flareon 8 day from begining
Vaporeon 88.8 aqua tail. My early fighter. 16 day from start.

My starter Charmander is my oldest mon :D

It's the jolteon I think I might have used Sparky on it may not be great in battle but it has attack wow so I called it Chihuahua because it's xs 2.6 kg but it could bite :p , with thundershock thunderbolt caught on the third of august, I didn't come by a lot of eevees back then

My starter Squirtle that I have evolved to a Blatoise (from 24 July 2016) followed by a Polygon from 2 August.

My oldest (bottom recent) is the same as my top CP (First on List):
Vaporeon 100% IV 3044 CP :)
evolved from a Eevee caught in the wild on 3 aug and 1st evolution i did (rainer)

Dragonite
3530 CP, 15/15/15 IV
Steel Wing x Dragon Pulse

Caught him back in September in Central Park. He's been good to me. ???

My oldest Mon is Snorlax from eggs when I was at L5 - L8... Last August

My first capture, Pikachu

My WP Vape, now lvl 34.5 in a gym, did not return after my last lvl up :), evolved like 3 days after I realy started to play (early September, lvl 3 I think, after 1 play session at the end of July). Did not know exactly what Appraisal was but since told me simply amazing I said go for it :). I knew about the trick and using Vape from a colleague (lvl 28 then, now retired) who told me that Vape is the mon to start battling.
Electabuzz, my first Vape counter :) (low kick, but still ok back then :) ).

After my starter Charmander (18.07.), Dratini (hatched on 23.07.), Flareon (caught on 24.07.), Pikachu (hatched on 24.07.) and Dewgong (caught on 24.07.)

The Dewgong i caught in my living room at then mind blowing ~800CP and it was the first Pokémon i battled with and my strongest for quite some time.
Not good for anything now but I'm a far too nostalgic person to ever transfer him.

Flareon was the first one i powered up over 1000CP and also one of my main mons in my early lineup.

Pikachu and Dratini just have really good IVs and i still haven't got anything better.
Also, at lvl 30 i still haven't evolved a Raichu(enough candy but don't wanna evolvey first pika) or Dragonite (not enough candy)

Mine is my first Squirtle (211CP). I searched and ran for that one since it was my first starter which popped up on my radar. That was in the good old times when the footprints still worked on 11 July. Kept that one for sentimental reasons and 211CP was quite a high catch for a Pokeball back then... and nobody knew or gave a shit for IVs :D

Second is my first ever 10k egg hatch: a shitty Magmar which ate all my dust and candies as I immediately powered it up to WP924 since it was by far my strongest attacker.
That was when WP800 Pidgeots ruled the gyms, a lvl4 gym was outstanding and the hardcore players were lvl18-21 :D

Level 6 Gengar with Shadow Claw/Sludge Bomb and 87 IV. After several evolves, he was the only one with the optimal attacking moveset... but after the most recent changes, it looks like it's no longer optimal for attacking... maybe time for the masher.

My three oldest mons are all from the day I started playing: first, my starter Charmander (10 CP), followed by the first Meowth I ever caught (also 10 CP), and the first pigeon I evolved to a Pidgeot (543 CP, and at one point a looooong time ago my best attacker). :-P