I just checked the prices on Numismedia and saw that when it comes to either the 1928 and the 1934s. The '34s appears to be more valuable than the '28.
ie: '28 in au50 and above is worth less than the '34s. For grades xf40 and below the price structure reverses.
That is curious. Unless for au50 to ms66 the population of the '34s is less than the '28. The '28 is "THE KEY" date isn't it?