Kienast had figured a total of 784 designs/creations but this number is flawed because varieties of certain medals were given an 'Opus' number when the piece should have actually been given a variety number e.g. K-19b. Kienast's number should be closer to 750 known at this time. Additionally, I believe there are another 10+ pieces Kienast 'identified' as Goetz works that are questionable. Add to this that there doesn't seem to have been any peer review regarding the authenticity, either based on provenance or stylistically, of these pieces I have identified. Remove these examples (paper to be written about these examples) and the total number hovers around 735-740.
In my research I have identified an additional 10-15 medallic pieces I know I can attribute to Goetz (another paper to be written to garner peer review). This would raise the total number back up to 760-765. This number is not set in stone and I imagine the number fluctuating +/- long after I'm gone.
So do we limit his works to only medals, medallions, plaques, plaquettes, coin patterns, wax seals (petschafts), tokens, and emergency money? What about all the jewelry and jewelry designs, do we want to count these too? I believe we do but perhaps with a distinctive break in the numbering.
I plan to present a proposal to logically renumber Goetz' works according to the year of creation. Goetz didn't do a very good job of consistent numbering for his works and Kienast's numbering wasn't much better. You currently have early pieces with late K-#'s and vice versa. Comparative and stylistic studies would fare better exhibiting the works in logical order. Again, I must present this idea to my peers in order to get a general agreement.
I'm not sure how you are perceiving the term 'opus' but it is quite simply what Goetz used as part of his numbering system e.g. Opus 5, Opus 6, Opus 7... It is the same number that Kienast used but with a 'K' for Kienast replacing the 'Opus'.
I hope this helped rather than muddy your understanding.
PS. I just had the opportunity to read your questions again aresgee and I see that I didn't catch the actual intent of your first question, "Is there a total count of medals manufactured by KG?" No one knows actual issue numbers. Guido, Karl's son, claims that all the records were destroyed in the Munich allied bombing raids of WWII, at least those stored in Karl's workshop. I don't know if this is true or not. I have had hints by family members that there is, indeed, a master list of medal counts but even if so, I would find it difficult to believe they would be very accurate based on Karl's record keeping elsewhere in his business. There is a researcher in Germany currently digging up numbers for Goetz medals struck at the Bavarian Mint. This would be helpful but still would not contain information for privately struck and cast pieces. I think I can say safely that in excess of one million pieces were created...only because the Hindenburg commemorative was struck in over a million pieces. Much further research is needed to formulate rarity for Goetz' works.