Your gun was built in 1927. It is not correct to refer to them in "grades." My favorites are from the mid 20's, and as has been noted, yours has escaped the typical uninformed disassembly of an Ideal, evidenced by damage to the inletting around the top strap. Also already noted is the quality of the steel of the barrels, and level of proof, indicated by wreaths of laurel leaves, not "palms." Actually , the lowest grade of barrels is no wreaths, up to, as has been stated, five in practice, seven or so in theory. I have seen a lot of La Manu barrels of high end examples, but never a set with more than five wreaths. Your tubes should be marked in mm just before the barrel flats with the finished bore size. This makes it very simple to determine if the bores have been honed, Fantastic, under appreciated guns.
Mike
