This is a model 1917 Army in .45 ACP. Somewhere around 170,000 were produced in 1917-1919 as substitutes for the 1911 during WW I. Half-moon clips were designed so empties could be easily extracted; you can also push out fired cases with a pencil or dowel.
It is true the serial number appears in several places aside from the bottom of the grip frame, but the latter is the official location. Depending on who you might ask officially, the answer may range from "it's ok, get the SN restamped" to "it's illegal to own, turn it in for destruction", as it is illegal to remove the SN from a gun. If this is a recent buy, personally I would ask for a refund; there are plenty of unaltered shooter 1917s out there. Hope this is helpful.