Bausch & Lomb serial numbers

Until 1942 Bausch & Lomb used a standard numeric sequence for the Serial numbers for their lenses.

Bausch & Lomb until 1942 (numeric)

Year	Serial nº		Year	Serial nº		Year	Serial nº
1876	1		1900	32000		1924	170000
1877	150		1901	33000		1924	175000
1878	350		1902	35000		1925	180000
1879	800		1903	40000		1926	185000
1880	1100		1904	45000		1926	190000
1881	1450		1905	52000		1927	195000
1882	1750		1906	57000		1928	200000
1883	2000		1907	63000		1929	205000
1884	2500		1907	69000		1929	215000
1885	3000		1909	76000		1930	225000
1886	3800		1910	82000		1931	230000
1887	4500		1911	86000		1932	235000
1888	5300		1912	89000		1934	240000
1889	6375		1913	95000		1935	244000
1890	7600		1914	98000		1935	247000
1891	9200		1915	104000		1936	250000
1892	10000		1916	110000		1937	260000
1893	11700		1917	120000		1938	270000
1894	13900		1918	129000		1939	280000
1895	17000		1919	135000		1940	290000
1896	20000		1920	140000		1940	300000
1897	25000		1921	148000		1941	310000
1898	28000		1922	155000		1942	320000
1899	30000		1923	160000

Bausch & Lomb from 1942 (alphanumeric)

From 1942 Bausch & Lomb used an alphanumeric code for the lenses, where the first letter encodes the year and the second letter (apparently) the class of lens

Year	1st letter
1941	A
1942	U
1943	M
1944	V
1945	B
1946	T
1947	L
1948	W
1949	C
1950	S
1951	K
1952	X
1953	D
1954	R
1955	J
1956	Y
1957	E
1958	P
1959	H
1960	Z
1961	F
1962	N
1963	G

2nd Letter	Lens class
A	aerial lens
F	photographic lens
S	lens for survey cameras