The labor market just did something that hasn't happened since the 1970s

Thursday's initial jobless claims came in stronger than expected, with 265,000 claims versus expectations of 269,000.

But the truly historic part of the report actually came three weeks ago.

"Today's release also includes revisions of both initial and continuing claims dating back to 2011," wrote Thomas Simons, senior economist at Jefferies.

"Most of the changes were relatively modest, but the most notable aspect of the revisions is that claims for the week of March 5th (3 weeks ago) were revised down to 253,000 which is, as far as we can tell, the lowest weekly claims figure since November 24, 1973."

Quick refresher, almost all economic data is subject to revisions as the respective agencies collect more information. For instance, quarterly GDP is revised twice after the initial release, and last month consumer credit for December 2015 was revised down to a growth of $6.2 billion from the month before after an initial print of $21.4 billion.

Revision or not, Simons finds the claims number to be worth noting.

"Considering population and labor force growth over the past 43 years, this is a remarkable statistic and it continues to suggest that not that much slack remains in the labor market," he wrote in a note to clients.

Simons expects that the continued strength of claims shows that the labor market is "grinding towards full employment."