Thanks for the measurements (despite the best efforts of your "autocorrect" software!)
When your father-in-law bought this vase it already had some age to it as it dates to the 1920s - 1930s. After about 1921 Japanese export ware tended to be marked with the word "Japan" or "Made in Japan" (as on yours in black) though some authorities insist that the use of "Japan" pre-dates the "Made in Japan" wording but in reality there was little consistency in this chronology.
By then most of this type of art pottery, which is generally referred to as "Satsuma", was being made in Kyoto which is most likely where yours came from.
"Satsuma" is both an aesthetic style and a type of earthenware pottery (with intentional crazing) and it's also a region. Originally all of it was produced near Kagoshima at the very southern tip of Kyushu on the southern island of Japan.
This Kyoto-made version is known as Satsuma-yaki or Satsuma export ware -it was produced exclusively for export to the West and was unknown domestically in Japan at the time.
These vases were produced in huge numbers and consequently, I have to warn you, this is not the expensive end of Satsuma pottery, unfortunately. Having said that, this 3-D or raised relief type does have its following of collectors and makes this piece a little more desirable.
The figures depicted are all holy men, or arhats, and the one woman in the center with the elaborate halo is Kannon, the goddess of mercy in the Buddhist tradition and equivalent of Guanyin in China (and the Virgin Mary in the Christian tradition).
It's all expertly decorated by hand, much of it in raised paste enamel and colored "jewels", an elaborate and tricky-to-do decorative technique that the Japanese call moriage -pronounced "mori-ah-gay". It's a process similar to icing a cake with a piping bag. The colored paste-like slip is squeezed through a tube.
As for the marks on the base, that top red character is really too chipped to read, but the bottom one is 山 or zan which is a common suffix for a Satsuma decorator. The mark could be
But it's not a decorator that's listed in any of my Satsuma references. That's not unusual, there were truly thousands of them, besides, identifying the decorator in this case is not going to make the vase any more or less valuable, it's just of curiosity value only.
Looking at comparables selling at present for this size, age and artistic merit Satsuma-yaki vase, I would give yours an auction/eBay value range of $130 - $200.
It therefore would have a retail value (if you saw it for sale in an antique store, say) of $400. This is also the replacement value for insurance purposes.
I do hope this helps!
Please let me know if I can be of further assistance with this, I would be glad to.