The only evidence we have of "Oswald" visiting the Soviet Embassy, that I am aware of, is the phone call made by an Oswald impersonator On October 1, 1963. That is the only call where the name "Lee Oswald" was given. In the call, the Oswald impersonator spoke in broken Russian to the embassy guard, saying that he had visited with an officer there on September 28. The guard suggested that the officer he had visited was Valeriy Kostikov.
If a person actually did visit Soviet Embassy that day, I believe it was probably an imposter, just like the "Oswald" that visited the Cuban Consulate was an imposter.
As for how the Excelsior newspaper got the information so quickly about the so-called Oswald visits, I suppose they could have gotten it from the Mexican police. After all, the Mexican police did hold Silvia Duran and a number of her friends for questioning, and did actually beat her, likely because she wouldn't admit to the charges made against her by Elena Garro, who was being held in "protective custody" at the time in a hotel. Garro's story painted Oswald as being a friend of Duran's and associating with her friends.
So the story the Mexican Police got from Duran was the innocent/real one (according to their understanding), where Oswald was there to get a transit visa. (Not to negotiate an assassination deal with the Cubans and Russians.)
Yes, I believe the Kostin letter was planted by the CIA in order to strengthen the evidence that Oswald had (supposedly) contracted with the Cubans and Soviets to have Kennedy killed. (Allegations made by Gilberto Alvarado.)
As for the comment in the letter about Azcue being replaced:
The CIA must have known about Azcue's replacement, or planned replacement. We don't really know if there was a timing issue as to the date of Azcue leaving, because when the Kostin letter said, "I am glad he has since been replaced," for all we know the CIA writer of the letter could have meant more specifically that the DECISION for his replacement had been made, and that soon the actual replacement will take place.
Or it could be that the CIA writer of that letter simply made a mistake... he might have merely assumed that the replacement had taken place prior to his writing of the letter.
Actually, I've never thought that Helms was one of the plotter. Though I suppose he might have been.
But even if he wasn't, I don't understand how what he said would contradict my beliefs as I've stated them here. Maybe you can explain.
First, Matt, I don't know if the following statement:
“When sending the photocopies, say that the letter of November 9 [discussed above] was not received by the embassy until November 18, obviously it had been held up somewhere.”
has anything to do with the Azcue replacement timing issue. The two dates, Nov. 9 and Nov. 18, might just be coincidences.
Even if that sentence does relate to the Azcue timing issue, I don't see how the instruction of that sentence, given to Ambassador Dobrynin, supposedly resolves the timing issue in the Americans' eyes. Especially in light of the fact that the U.S. knew precisely the date of the letter and the date the Soviets received it, a fact that apparently the Russians were aware of (since they knew of the U.S. mail intercept program).
What details? The Azcue replacement timing issue dates?
The CIA knew that Azcue was going to be replaced. So why wouldn't the Soviets have not also known that?
With the Azcue replacement date in hand, and the Kostin letter in hand, the Soviets had all the details that you've pointed out. No mole needed to get it for them.