simply a capital K with a horizontal line under it, the same width as the K.
I can’t find any information about it.
A little perseverance pays off.
The previous alert can be cited with the URL: http://www.kashrut.com/Alerts/?alert=A4324
If the product is Bob’s Red Mill, the underlined K means Kehilla Heart K from Los Angeles, Rabbi Teichman
Is the ® a good hechsher?
Depends on your definition of Orthodox.
The ® (Orthodox Rabbis) isn’t as accepted as the © (Orthodox Chachomim).
How about the ™ (Temidi Mashgichim)?
I believe that is only accepted by the Ⓞ (Open Orthodox).