It seems to me both Callandor and the Stone were the last major One Power artifacts, born of a necessity perhaps greater than the DO himself. It also seems like the Choedan Kal were probably made sooner, though it's again hard to be clear on the data we have. We do know, however, that a critical reason LTT acted unilaterally at the Strike on Shayol Ghul was that the areas where the access keys had been secretly hidden had both fallen to the Shadow, which implies they were at or near completion by then.

My impression of the Rhuidean scene is that Callandor (and perhaps much else... ) were fresh from the mold then. After all, the plan all along was to ensconce it in the Stone to await the Dragon, so clearly that hadn't happened yet, either because the Stone itself was still incomplete or simply because they hadn't yet had the opportunity.