Here is a bit more precision on Laporte’s working dates.
As you know he was a cutler, first registering a mark on 10 December 1825, erased 30 December 1853. He registered his mark again on 24 February 1853, erased 26 May 1863, because he changed addresses from 20 rue des Filles-St-Thomas, to number 12 on the same street. Thus Laporte worked 10 years longer than you supposed.
See Arminjon, v. I, no. 00887, p. 119.
Laporte supplied many high-end French makers, including Odiot. He won a bronze medal at the Paris 1939 Exposition of Industrial Products, the jury remarking that his work was especially prized by the foreign market. He won medals at that same Exposition in 1827, 1834, 1839, and a medal of honour in 1855.
See David Allan, p. 307.
His successor was Édouard Corvasier.
Are you aware that there are 2 Mercury head marks for French export items? The first, was in use 11 July 1840 until 1 April 1879. The second Mercury head mark (1879-1973) looked slightly different, having a 1 to indicate 950 standard silver to the left of Mercury’s neck. Your photo is too unfocused to see which Mercury head we’re seeing. But if it is the first Mercury head, this clears up any confusion regarding date of manufacture and marking.
See Tardy, pp. 204-205.
If it is the second Mercury head, Odiot might have marked this stock of blades whenever they were mounted onto one of their patterns for export.
As for the crown, to me it most resembles a Russian Orthodox bishop’s crown rather than a Russian Imperial crown. Again, better focus would help here.