Quote Originally Posted by jeking View Post
That's a lot of digging, thanks! I'm not comfortable testing the untested code on this live site. But I do understand the problem much better. I'll get back with my client with some options for him. I'll try again to convince him to use Model Numbers.
Model number won't specifically resolve the issue and is not specific to causing the observed response(s).

Does the store perhaps use products_sku and applied a suggested implementation that was posted earlier in this thread? Basically, if search for EP4_DB_FILTER_KEY to see if it is used outside of the core files in the root of the admin, the extra_functions folder of the admin and/or the admin's modules folder.

Note for others, the plan is/was that if an alternate filter option were desired/to be used, then it be added to the selection list in the configuration menu. The earlier "add-on" was just that, an additional set of code to show that it could be possible and how it might be implemented.