At least three of the problems must be originals; the remaining may have been published before.
E. L. Lequesne, S. Loyd, Rosenthal
S. Loyd is both a judge and a competitor in the problem tourney. As he also won a prize, it would have been desirable to know how his set was judged. No such information has been found.
The congress book content was published in parts, which were sent to subscribers as they were printed. According to The Era 1868-07-05 the part that concerned the problem tourney had, to the chess editor's knowledge, not yet been published.
In the chess column of The Era, 1867-08-04, the following communication from a pseudonymous contributor is printed:
The chief event since the finish of the Tourney has been the decision as to the prizes for Problems. The Committee appointed to examine the competing sets was to consist, I am told, of the four winners of the Tournament for the Emperor’s prize, but they fell to squabbling, and three of them declined to act. Finally, I believe, the examination devolved on Kolisch and the young English player, De Vere, who were said to have executed their very onerous task with skill and impartiality. The result of their labours has not transpired.As the names of the judges were published already in the congress announcement, the account is probably a misunderstanding, at least partially.
The congress book does mention that the Problem Committee decided that the prize-winning problems should be submitted to additional verification by the four winners of the Grand Tournament. It doesn't say anything more about the details of this activity except that the result agreed with that of the problem tourney judges. This may be the origin of the passage quoted above.
Problems known to not be originals are indicated with a
1 Prize: C. Bayer
Key: 1. Sd6
Source: Congrès International des Échecs, p. 347, prb. I:2
2 pr. set, Le Palamède Français, 1865
Key: 1. Sg3
Source: Le Palamède Français, 2/13 (Sept. 1865), p. 44, prb. 88
Key: 1. Be2
Source: Congrès International des Échecs, p. 349, prb. I:4
1 pr. set, British Chess Association, 1862 (London)
Key: 1. Sg×f4
Source: The Era, 25/1263 (1862-12-07), p. 5, prb. 440
2 Prize: S. Loyd
Key: 1. Ba8
Source: Cincinnati Dispatch, (1858-09-05), prb. 45
Key: 1. b×a8=N
Source: Congrès International des Échecs, p. 351, prb. II:2
Key: 1. Qa8
Source: Congrès International des Échecs, p. 353, prb. II:3
Key: 1. B×a6
Source: Congrès International des Échecs, p. 353, prb. II:4
The Excelsior problem.
Key: 1. b4
Source: The Era, 29/1501 (1861-01-13), p. 14, prb. 337
3 Prize: E. Grosdemange
Key: 1. Bc1
Source: Congrès International des Échecs, p. 355, prb. III:1
Key: 1. Rc2
Source: Congrès International des Échecs, p. 355, prb. III:2
[+] = Faulty: No solution
Key: 1. Ra5
Source: Congrès International des Échecs, p. 355, prb. III:3
Key: 1. Se4
Source: La Nouvelle Régence, 5/3 (Mar. 1864), p. 95, prb. 237