I downloaded and installed Speccy and then opened it. The first thing I noticed was that the Operating System (Win 10) Key it gave is different than what I got from two other softwares. Speccy starts the 25 letter-number combination as T49TD, while both ProduKey and Belarc starts the combination with YTMG3. Does ProduKey and Belarc get their information from another area than Speccy, and which is correct (if any are correct).
Speccy must be different somehow.
I too had you issue, Belarc and ProduKey gave the same, and correct, key while Speccy gave something completely different.
However, with Windows 8 and the last few Speccy versions, it has agreed.
I haven't tested it with Windows 10 yet.
If you upgraded to 10 from 7, 8, or 8.1 before TH2 then Microsoft issued you with a new Product ID and a new Product Key as part of the upgrade.
I believe that the old key, from the original build, is still retained on your system somewhere - this could explain why you are getting two different numbers, they are being read from different places.
My new Win 10 Home product key also starts with YTMG3-
(I've read somewhere that all Win 10 home keys are the same, but the pro & enterprise keys are different?)
My old win 8.1 key started with 7DMNP-
(Both read from speccy).
If you upgrade now, after TH2, then you retain your existing key instead of getting a new one.
It shouldn't realy matter in most circumstances.
Microsoft is changing to the use of online activation, reading the info straight from your machine instead of entering the Product key.
So if you do a clean install on the same machine you no longer need the key.
(I for one will still be keeping a note of the key though.)
More on Win 10 product keys and automatic activation:
http://www.redmondpie.com/windows-10-product-key-and-activation-how-to-find-it-and-how-it-works/