You can sometimes use clues like this to help arrive at the age of furniture.
The two oak planks in the top of this refrectory table from France have shrunk at different rates. The table appears to be from the 1600’s, however if that was the case we would expect this joint to be significantly more worn as it on the top and frequently touched by human hands. So we suspect tha the

the rsblr is more recent. However there
is definitely some age as these old  planks would have taken 50 to 100 years to shrink evenly but consistently in this fashion. So our guess, early 20th century, possibly a little later.