Back in November 2018, I got my Meltan from research (not Meltan box). I remember calculating him and getting 96% 14ATK 14DEF 15HP. I didn't power him up or anything, let alone touched him since I got him. Around a week ago, I tried looking at how much CP Melmetal would be if I evolved him. For some reason, any IV calculator that exists won't show anything when placing the details down ("No possible IVs found for those values"). I tried everything that I can think of and nothing worked. I'm sure it's not me, I'm entering the details correctly and double checking everytime. It seems as if for some reason no calculator can give me answers. I also tried downloading apps to calculate IV but still nothing. I will list the info of the Meltan so you can check for yourself:
457 CP (lvl15)
75 HP
1,900 Stardust
14/14/15 (only HP is 15)
6.49kg
0.18M
(I added the height and weight for lolz).
As I recall, Meltan has its stats slightly altered a few months ago. The one you got sounds it escaped the alteration for some reason, therefore the up-to-date IV checkers won't recognise it.
To correct it, all you need to it is power it up once, but if you suspect it's a 96% then it's hardly going to be a waste. Evolving it to Melmetal will also correct it.
Don't need to power it up if you previously IV checked it and wrote it down. Base stats changed, but IVs are the same. The old CP remains the same until you do something with it. You could maybe try putting it in a gym even.
You can use GamePress's CP calculator:
https://pokemongo.gamepress.gg/cpcalc#/
You can manually enter the IV and level info to see what it will power up to.
Edit:
https://www.reddit.com/r/TheSilphRoad/comments/aefk1z/question_meltanmelmetals_new_base_stats/
I just added a row for the old base stats with a slightly different name in one of my spreadsheets. With old base stats, 14a/14d/15s at level 15 does indeed have 457 CP and 75 HP.
