Sun has a penchant for renaming (and retroactively renaming) products: witness the renaming of SunOS 4.1.4 to Solaris 1.1.2, etc. Fortunately, it also likes to continue existing naming schemes for consistency.
The earliest SPARC systems had names in the style of the Sun 3 systems: 4/110, 4/330, 4/600. With the debut of the SPARCstation 1, Sun introduced a new naming convention but continued, for a time, to assign the older-style names, as well. For example, a SPARCstation 1 is also a 4/60, and a SPARCstation 2 is a 4/75. The older machines were then officially renamed SPARCstation 330, and so on.
Sun still likes to assign different names to essentially identical products. Rebadging a "workstation" as a "server" is common: Sun ships the system without a frame buffer and christens it a "server." Therefore, a SPARCserver 10 is a SPARCstation 10 without a frame buffer; an Ultra Enterprise 2 is an Ultra 2; and so on. With the mere addition of a frame buffer plugged into the expansion bus, the system becomes functionally identical to its sibling.
This document will refer to the names used at the introduction of each product. Incidentally, Sun stopped assigning the older-style names around the introduction of the SPARCstation 10. By that time, it had other naming problems to worry about, such as the number and speed of the processors in such configurable machines.