This list contains extensions and their Type and Creator for vintage Mac OS (System 9 and below). I'm populating this list as I encounter them, so it's not a very long list. There are other 
resources available, but some of the files listed here might not be there.
| Extension | Type | Creator | Comment | |-----------|------|---------|---------| | `.dsk` |`DDim`| `DDp+` | DiskDup+ Image | `.image` |`dImg`| `dCpy` | DiskCopy 4.2 Disk Image | | `.img` |`rohd`| `ddsk` | DiskCopy 6.3 Disk Image | | `.img` |`dImg`| `dCpy` | DiskCopy 4.2 Disk Image | | `.toast` |`GImg`| `CDr3` | Toast CD Image | `.toast` |`HImg`| `CDr3` | Toast Hybrid CD Image
I use DropAttribute to change the files. Below is a snapshot of the Mac OS Type/Creator Database google sheet.
snapshots/macos_types