The 27 is a full sized machine, the 28 is a 3/4. Your handcrank is a 28. Not all 28s were handcranks tho.
To tell the difference between a 27/28 and 127/128 check the shuttle. Is there a little button that you press to lift the shuttle out? If not, it's a 27/28, if so, 127/128.
:) Pretty new babies!! They take a standard 15x1 needle, you don't have to buy Singer needles...any brand will work.