For R&D purposes, I would very much like to get my hands on the circa 1991 Microsoft LAN Manager Network Device Driver Kit which was meant to support the development of NDIS 2.0 drivers. While it is obvious that some kind of development kit for NDIS 2.0 drivers must have existed, the exact name is actually known thanks to the Q80562 KB Article.
That same KB Article also mentions MTTOOL, a test tool that sounds very useful, but unfortunately I’ve not been able to find it anywhere. The tool itself would be helpful even without the rest of the kit.
The closest thing I could find is a 1993 NDDK (Network Device Development Kit) that supports NDIS 3.0 drivers for the Windows for Workgroups 3.11 environment. While the NDDK is valuable on its own, it is quite different and not immediately useful because it is oriented towards Windows NT and 32-bit environments, unlike the 16-bit NDIS 2.0 which supported DOS and 16-bit OS/2.
The old LAN Manager NDDK seems to have fallen through the cracks of the post-IBM-divorce chaos at Microsoft. It wasn’t documented in the older Microsoft Programmer’s Library and by the time MSDN was rolled out, the NDIS 3.0 NDDK was current. And because OS/2 had been disowned by then, Microsoft probably saw no need to widely distribute the older NDIS 2.0 kit.
Which is ironic because although NDIS 2.0 development might be finally dead now, it was not a few years ago, with Intel offering an updated DOS network driver package as late as 2019. The newest NDIS 2.0 driver in the set is dated December 28, 2015, which means NDIS 2.0 survived even past the Windows XP era, leave alone Windows 9x or Windows 3.x!
Update (June 23, 2021): Less than 3 months later, the 30+ year old NDDK popped up. It is now available here.