WinHelp annotation
From Just Solve the File Format Problem
WinHelp annotation files (.ann) are annotations to HLP (WinHelp) files. These in principal use the same structure as the HLP files. Therefore, these are not pure text files, but they are rather binary files. The annotation parts themselves are embedded as simple text.
Identification
Files start with hex 3F 5F 03 00
like WinHelp samples and at offset 0xD4 with bytes 62 6D 66 01 00
.