
Telegraph block instrument; South Eastern Railway; Walker's patent No. 245
1855
1855
1845-1855
circa 1900
circa 1850s
1821
1905
1903
1890
1839
1901
1846
1901
1895
1878
1881-1900
1934
1875-1877
1830
1826
1831
1872
circa 1900
circa 1850
circa 1848
circa 1880
circa 1900
1875-1890
1846
1801-1892 (prepared); 1946 (element replaced)
1801-1892 (prepared)
1879
1900-1911
1894
1854
1903
1878-1900
circa 1840
1801-1819
1904
1801-1900
1830-1850
circa 1801
1830
1825-1871
1801-1900
1871-1900
1820
1801-1900
1801-1900
1870-1880