Supro(s)
Page has mentioned numerous times since the 1970's that he used a "small Supro with a 12 inch speaker" on the first Led Zeppelin album and for the Stairway to Heaven solo. This has open numerous debates and myths about what model he actually used. The Supro he used on LZI is believed to have been the Supro he bought in 1961 or 1962 with Albert Lee. The only 12" loaded Supro at this time was the 6973 loaded 1624T. It fits Page's description, it's small and has a 12" speaker. The amp is easily capable of the tones.
On the other hand a few years ago a Page gave the Rock and Roll Hall of Fame another Supro, which they displayed as being the LZI/Stairway Supro. After being researched by a few people it was determined it was the 6L6 loaded 1690T Coronado modified with a 12" speaker. A stock Coronado used a 2x10 setup. While it would match Page's 12" speaker comment it sort of creates an issue because Page has never mentioned the Hall of Fame Supro being the one he used and there has been some speculation it is the one he bought after the LZI/Stairway Supro was smashed as mentioned in the 1977 Guitar Player interview. The 1690T in the Hall of Fame was also modified with an extra switch believed to switch the tremelo circuit in and out which adds an increase in gain.
There are other models that have swirled around with his name, the Thunderbolt being the main one which many have ruled out for at least being the LZI Supro. If the LZI Supro was the same one he bought in '61 then the Thunderbolt is definitely ruled out as it wasn't released until 1964. In addition to that the Thunderbolt used a 15" speaker which wouldn't match up with Page's description of a 12" speaker. A model with a 6x9 speaker has been mentioned as well, once again though doesn't match his 12" speaker description and there were numerous 6x9 loaded Supros. Based on Page's 12" speaker quote, it was either the 1624T or the 1690T in the Hall of Fame. That's about as definitive as you'll get.
As far as how much studio use the Supros seen is anyones guess. LZI and the Stairway to Heaven solo is the only time he mentions anything specific. However when he mentions using a Supro on the first album in the 1977 Guitar Player interview he replys like this; "I was using the Supro amp for the first album and still do." Make what you will of that.
The 1690 from the R&R Hall of Fame.