The "Batta-Piatigorsky" cello at the Metropolitan Museum of Art is an example of one of Stradivari's smaller sized cellos, which were made possible due to an advance in string making around 1665, in which gut strings overspun with metal wire were developed. The smaller cello was easier to play and had better sound quality.
The "Batta-Piatigorsky" cello is named for its two most famous owners. First, the Dutch cellist Alexandre Batta, who purchased it around 1836 and used it for most of his career, and later the great Russian cellist Gregor Piatigorsky. A full provenance is available here. Mr. Piatigorsky said the following in his biography:
"I played the 'Batta' for a long time before appearing in concert with it. In solitude, as is befitting honeymooners, we avoided interfering company until then. From that day on, when I proudly carried the 'Batta' across the stage for all to greet, a new challenge entered into my life. While all other instruments I had played prior to the 'Batta' differed one from the other in character and range, I knew their qualities, shortcomings, or their capriciousness enough to exploit their good capabilities to full advantage. Not so with the 'Batta,' whose prowess had no limitations. Bottomless in its resources, it spurred me on to try to reach its depths, and I have never worked harder or desired anything more fervently than to draw out of this superior instrument all it has to give."
Here are some photos that I took of the instrument, again somewhat constrained by display and lighting: