I am not certain it is not before 1900 but that style roofing hammer is very common and a modern (post industrial revolution) product not something from colonial times. Cedar shingles were real popular in the late 1800s through the mid 30s when Asphalt took over. By the late 1800s Asphalt was in use and has generally replaced Cedar on most construction. This type of tool is specific to wood shingles you drive the nails with the hammer head, trim them with the hatchet part and pull bent nails with the slot. I have used them to install wood roofs myself and they are a handy tool. As you can see they still make roofing hammers that look pretty much the same. My point was it was not an axe it is a roofing hammer sometimes called a roofing hatchet. An axe has a long handle and is swung with 2 hands. A hatchet is a one handed tool with a short handle like under 16 inches long. A true hatchet does not have a hammer or nail puller on it but may have a blunt end for pounding tent stakes into the ground. The type of shingle these are made for is a sawn shingle or a split shingle which is now called a shake Sawn Cedar shingles became cheap when the West was exploited for timber. Late 1800s to mid 1900s. Certainly a few of these roofing hammers were around before that time frame but the mass production of them would be mid to late 1800s to early 1900s. You can still buy sawn cedar shingles as well as split cedar shingles but the scarcity of quality old growth Cedar makes them more expensive then Asphalt. I see shakes used on high dollar new houses but have not seen sawn shingles on a roof in a long time but see them used as siding on some newer houses. .
...on average I dig 5-20 picks and as many axe heads a season,and I too,use the wire wheel 
A light coat of tung oil with stop further rust as well
