Great question, meb.
There are definitely items in the database that need separate entries for MK 1, 2, 3, etc -- The Elektron MK2 and MK3 products come to mind: there are meaningful changes between each revision, to the point where some owners agonize over whether or not to sell their current MK1 Octatrack (for example) to fund moving up to the MK2 or MK3.
But in the case of the Revox A77, a product discontinued almost 50 years ago, their use of model revision designations seems to be more old school: they were making subtle changes to the product almost every year, in the name of continuous improvement, aesthetics and/or parts availability, and not making much of an effort to market these changes to customers.
For things like this, I ask myself these questions:
Q: Would distinguishing between revisions help when submitting items to an Artist?
A: Looking at the current A77 submissions, I'd say no -- many of the submissions are from mentions of the A77 in interviews or official gear lists, rather from photos or videos. It doesn't look like many of them (if any) specifically mention whether they used a Mk2, Mk3, etc... they just say "We used a Revox A77".
Q: Would this help users shopping for gear?
A: I'm no tape expert, but from what I can gather about distinctions between revisions, its way more important to find an A77 that has been well maintained and calibrated, than it is to make sure you get a specific revision. The MK1 may have been slightly noisier than the MK2, as a theoretical example, but that was back in 1968 -- in 2024, the machine that was taken care of or recently restored is going to be the less-noisy machine, the few parts that distinguish between a MK1 and MK2 may have been replaced or upgraded over the years anyway. Also, it looks like there were some interchangeable parts between each Revision, so (in theory) machines still in operation today might have a capstan from a MK3, the body of a MK2, a meter from a MK4, etc.
3. Would community members who own this gear care about these distinction?
A: Some might, for sure, but if the Artist submissions are any indication, a lot of artists actually using these machines don't really care to mention the revision. There are some clear aesthetic distinctions between some of the revisions, as you point out, but I don't think any of the machines had "MK II" or "MK III" actually written on the unit anywhere, you have to look up your serial number and/or ask a tape forum to figure it out. In some quick research, I'm seeing people who have owned an A77 for years asking for help figuring out which revision they've been using.
So based on the answers above, I'd vote to keep this one simple as "Revox A77" and let it apply to all revisions... but what do you think?