Steampunk music can be identified on a five point scale. Depending on how many of the criterion the band fills, the more steampunk it is. Bands on the list below should fill at least 2-3.

• 1.They call themselves steampunk.
• 2. Old fashioned dress or style.
• 3. Classical instrumentation elements.
• 4. Fictional (preferably alternate history) backstory.
• 5. Steampunk (sci-fi/historical) lyrics.

Dieselpunk is generally from the twenties through the end of WWII. This era is depicted by the wearing of Fedora hats and other such items of costume from the 1920’s through 1949. While there is no place devoted specifically to Dieselpunk, I will allow those bands to be listed here, with the proviso that they be labelled as   Dieselpunk Bands.

http://steampunk.wikia.com/wiki/List_of_steampunk_bands