In the 19th century, it was common practice for operators to number their
rolling stock from 1 to the number corresponding to the number of items,
ostensibly to make accounting easier. This meant that when a vehicle was
lost, the next vehicle obtained took the lowest available number - much to
the confusion of later historians !
The Victorian Railways had numbered their passenger carriages in such
manner, but subsequently modified that system - in the late 1880s they
separated bogie cars from fixed wheel (bogie cars being given a "double"
letter code - eg. 19 A became 19 Aa), then in the late 1890s they separated
carriage types (285 AVav became 1 AVav, etc.), and in each of these cases
the numbering started from "1" again - a fairly unique situation amongst
railways ! This also makes for interesting but frustrating research !!
Closer to home, the Victorian provincial tramways (Ballarat, Bendigo,
Geelong) were great recyclers of fleet numbers, some being applied to no
less than *four* different tramcars in a single city. On the other hand,
there were exceptions - for instance, Ballarat did NOT re-use fleet numbers
1 to 10.
[Photos from BTM/SEC archives: Ballarat trams No. 22 (1st, 2nd, 3rd, 4th)]