Windows NT 3.1 build 528

Windows NT 3.1 build 528.1 is the second RTM build of Windows NT 3.1, released two months after the original RTM (build 511). It introduced support for the Alpha architecture and included the first set of bugfixes for build 511, which were also released separately in the form of a service pack. Later service packs, namely SP2 and SP3, kept the same build number.

Compaq OEM version
There is also a Compaq OEM version of this build dated to January 1994 which was dumped by Internet Archive user nt351 on 15 April 2019.

It contains a modified setup boot disk image (interestingly called BOOT350.IMG) and some additional files, and is an all-in-one disc containing both client and server builds in languages German, English, French and Spanish. The modified setup boot disk allows the user for choosing the language and SKU.

However, all registry hives on the CD are encrypted and a Compaq License Diskette containing an encrypted decryption key is required to install. The key encryption key is a floppy-specific product key that is requested after reading the Compaq License Diskette by SETUPAPP. So far, no image of this floppy has been leaked, making it impossible to install this OEM version.