No, the Warren Commission Exhibit Nos 275 & 276 had already been assigned elsewhere (during Mr Robert Oswald's WC testimony in February), and the assigning of Ruth Paine Exhibit Nos 275 & 276 was still eight days in the future.
The rods submitted to the lab 3/15/64 were marked (for whatever non-WC-related reason) with the numbers 275 and 276. This is what necessitated the later blatantly contrived creation of Ruth Paine Exhibit Nos 275 & 276. The 'marking' of two curtain rods as such was the entire point of the testimony session in Irving 3/23/64
And off to Tinfoil Fantasyland we go...
Ruth Paine's house, 3/23/64
Mr. JENNER - May we take these curtain rods and mark them as exhibits and we will return them after they have been placed of record?
Mrs. PAINE - All right.
Mr. JENNER - Miss Reporter, the cream colored curtain rod, we will mark
Ruth Paine Exhibit 275 and the white one as Ruth Paine Exhibit No. 276.(The curtain rods referred to were at this time
marked by the reporter as Ruth Paine Exhibit Nos. 275 and 276, for identification.)
So the two rods taken from Ruth Paine's house are marked Ruth Paine exhibits 275 and 276
The two curtain rods on the dubious DPD report are marked 275 and 276
Common sense would tell us that these are one and the same rods.
But not in Tinfoil Fantasyland.
In this other realm two rods are submitted to Day by Agent Howlett. How they came into Agent Howlett's possession cannot be explained. (Back in the real world Howlett takes charge of them at Ruth Paine's house and delivers them to Day)
Someone has scribbled the numbers 275 and 276 on the rods for no known reason, this cannot be explained. (Back in the real world they are "marked" for identification. That's why Day bothers to mention it.)
Rather than just ignore these random numbers or erase them, a massively elaborate hoax is put in motion, the reason for which cannot be explained. (Back in the real world the "hoax" is merely an extension of Ruth Paine's testimony).
The Hoaxers (Paine, Jenner, Howlett and "Miss Reporter") have all learned their parts.
A complex choreography is performed as they move through the house asking and answering various questions, taking various measurements and picking up exhibits as they go along which are carefully marked, starting at "Ruth Paine Exhibit 270". They have to make sure that by the time they get to the curtain rods they are ready to use the all important numbers - 275 and 276.
"But why?", you may ask.
"Why do the curtain rods have to be marked 275 and 276 just because some unknown person scrawled these numbers on the ones submitted to Day?"
"...ssshhh, nobody will ever know...""Hold on a second", you say in a confused tone, "What's the point of this massively elaborate hoax, the specific goal of which is to mark these curtain rods 275 and 276, when there's an official document stating these rods were already submitted eight days ago? It just doesn't make any sense".
"...ssshhh, this is Tinfoil Fantasyland. Unfold the wings of your imagination and fly away...""But why not just throw the "TSBD rods" away immediately? Why submit them, then throw them away?"
"...fly awaaaay..."As you might have guessed Alan, I'm not too impressed with your answer.
Here's a bit of Occam's Razor for you - the submission date is wrong.
One one hand a massively elaborate, totally pointless hoax.
On the other - a wrong submission date.