I was looking through my carts and then I found this:
This was the back label for Zoda's Revenge: StarTropics II. The only change I see is the added "-1" and the removal of the "Rd. Ⓜ". I remember this being a later release and sure enough it came out in March 1994. So, I thought maybe Wario's Woods would have the same label and it does (
https://www.ebay.com/itm/153624555584).
This is when I discovered bootgod has release dates, a filter for games with save batteries, and back label codes (
http://bootgod.dyndns.org:7777/search.php?region_op=%3D%60%4... ). Circling around to your question about the first three save battery games it looks like you are correct with Ultima: Exodus releasing in February 1989.
We can use this to help figure out some dates. Labels 1 and 2 were Zelda 1 only, so bootgod won't be able to help yet. I noticed you asked if Label 1 appeared on anything besides the 5 screw zelda. There are two revisions of Zelda 1 with 3 screws and label 1, but no Zelda 2s. One doesn't have the "Made in Japan" (
https://www.ebay.com/itm/202794358106) and one does (
https://www.ebay.com/itm/283636423678). As there are several revisions with label 1 and a rare few with label 2, I would think that the 1/2 switch would be Spring/Summer 1988.
As you said the 2/3 switch was probably in Summer 1988 to get ready for Zelda II.
For the 3/4 switch we can start using bootgod. Ultima: Exodus (February 1989) only comes with the oval SOQ and label 4. The 3/4 change happened one revision before the SOQ change on both Zeldas (Zelda II example:
https://www.ebay.com/itm/401912187898). It seems the SOQ change was also in February 1989, so this change was probably Winter 1988/89.
Bootgod lists the change for 4/5 as between Wizardry: Knight of Diamonds (April 1992) and Baseball Stars II (July 1992). I double checked ebay, and all Wizardrys had label 4 and all Baseball Stars IIs had label 5. So, the change seems like it happened Summer 1992 (as you said).
Back to the 5/6 change that I just found, the next earliest game after StarTropics II is Kirby's Adventure (May 1993) which I found with (
https://www.ebay.com/itm/123929053260) and without (
https://www.ebay.com/itm/163893543255) the "-1". So, the change probably happened sometime between Fall 1993 and Winter 1993/94.
Going through the back label column on the Bootgod list there is one outlier (excluding prototypes), "Overlord" (January 1993). Checking ebay I found it with two different labels. The first is Label 4 (
https://www.ebay.com/itm/283508291641) which is a bit strange since the 4/5 change happened half a year earlier. But even weirder I found a unique back label (
https://www.ebay.com/itm/113772050051). This one isn't even gold, it's gray. It's text is similar to Label 5, except it only has the english text, there is no "Rd.", and the "NES-USA/CAN-1" now says "REV-A". I thought this might be a publisher thing, but Virgin Games released Greg Norman's Golf Power (July 1992) not long before and it only comes with the normal Label 5.
Here is a summary of my dates:
Label 1 - Summer 1987 - Spring 1988
Label 2 - Spring 1988 - Summer 1988 (rare)
Label 3 - Summer 1988 - Winter 1988/89
Label 4 - Winter 1988/89 - Summer 1992
Label 5 - Summer 1992 - Winter 1993/94
Label 6 - Winter 1993/94 - Winter 1994/95
Label 7 - January 1993 ("Overlord" only)