A few interesting examples and baselines which can be used when making an assessment of quality. You will need to click each photo to see the enlarged verion and associated comments.
Poor to low quality
This piece speaks for itself. Particularly evident is fitting which uses the lowest quality of materials.
For anyone who really is looking to have more control over the complete look of a piece, here is an excellent article by Architectural Classics entitled How to Age Brass – Ultimate Guide. Definitely worth a look if you are interested in the specific process.
The link is: http://www.architecturalclassics.com/blog/how-to-age-brass/
There is also a few good books on amazon on this subject as well:
The specialists guide to Chinese antiques is Stephen Fry proof thanks to caching by WP Super Cache