wrong firmware / ipsw restore problems iphone 5 A1429 ios 8.4

hi

i have two identical iphones 5 / A1429

i have downloaded the ipsw and I'm pretty sure that i downloaded the correct one which is

iPhone5,2_8.4_12H143_Restore.ipsw

i have updated my first iPhone successfully

but when i try on my second iphone i get this frustrating message

the iphone could not be restored because the firmware file is not compatible

just some thoughts and things i tried :

-the ipsw is not corrupted because the first iphone got restored successfully

-updated my itunes to the latest version

-using PC X64

-the ipsw / firmware file is correct because the first iphone got restored successfully and both phones are identical

-tried disabling antivirus software still no luck

-tried removing all other usb devices still no luck

-rebooting pc still no luck

-tried updating on mac no luck

-tried updating directly from itunes , after the download finished the phone rebooted and i got the progress bar on white screen reached the middle and screen goes black , waited for it to come to live again but it didn't , tried pushing power button , connect to itunes appear , tried connecting to itunes message is : iphone needs to be restored , start all over again , itunes update does the same mid-progress bar shutdown , while trying by holding shift and selecting ipsw file to update says firmware is not correct

does any body have some clue of what is happening

thanks a lot in advance for any help