How to efficiently delete large number of duplicate photo copies from LRc folder “All Photographs”?

A couple of extra points-

The 'All Photographs' is simply an almalgam (a list) of ALL photos that the Catalog knows about (ie. have been imported to the Catalog).

It may be possible that the photos you consider to be "Duplicates" are located in a different FOLDER, which you can check by highlighting one 'duplicate' file and a [Right-click] > [Go to Folder in Library] will show you where it is located on your hard-drive. This may make it easier to 'find' those duplicates.

There must be some differences with the "Duplicate" files (different filename, filetype, editing, etc) such that LrC did not recognize them as "Duplicates" although they may be visually similar.

(The Import option [Don't import suspected dulicates} does not 'Delete' anything- it will only refuse to Import identical files to the catalog.)

Well first off do you have any mechanism to easily find them? For example, on the Mac OS if you put a file (any kind) into the same folder that has the same name (unless there is no part of the process to warn you), it adds a "-2" onto the file name (myphoto-0034.jpg would be myphoto-0034-2.jpg). The one problem here is if you were to inadvertnelty delete a file that you did NOT want to delete.

It is important though, as stated, that these need to be in the same folder. If you've evern cycled through your camera's numbering system, you can easily have images in your catalog with the same number but are very much different images.

If you can visually see that you have duplicates, you can select the one you do not want and tap the "x" key to Reject that photo. Then settle back with some nice wine, great music, and "x" away. Then you can do a search for all "x" photos, select all, and delete them from your system. Then strat up again and do several hundred more.

Sorry, best I can do.