No, but there's probably many similar solutions that would fit:
Along with starter solutions that could easily adapt.
The concept is easy regardless of where you start. 90% of the time you spend on "turnkey" stuff anyways is usually customizations specific to the install.
When I was little, my father was a gunsmither had a gun shop and this brings me happy memories .
I agree with Mike, you can start with a starter solution, like FM Starting Point and just add fields like serial number, a container for the user permit scanned image, repair instructions, etc.
You can create a new module for repair orders, which would track repair time, parts used, pictures (they are VERY important), etc.
The sales process can be handled with the file as it is.
Hope it helps.
I haven't seen anything, but I've built a simple FileMaker-based bound book. At some point, I'd love to expand it to cover transaction such as ordering from a distributor and generating receipts, but haven't had the time to devote to do a proper job.