Try lighting a match near the fireplace end after you turn the gas key. Also, if there is a basement, try and see if there is a shut-off valve located under the fireplace.

It's hard to judge from the photo, but it appears there is a threaded cap on the end of the gas line.

It may be that former owners had a set of gas logs or had a gas fire starter.

Looking at the amount of charring behind I can guess that the pipe was part of a gas lighter for wood burning. I would be more concerned about the missing mortar on the fire brick base and that black "caulk" you see behind looks like high heat mortar caulk. definitely get that inspected before using. Bonus though - with the gas pipe, you can add a gas log set.

Try following the gas pipe to its source. Best to have the gas turned off or capped at the meter. With respect, lighting matches to detect natural gas is like checking your vehicle's gas tank with a match!

If you're planning a wood fire, have the fireplace and chimney checked first. A friend set a toasty hours-long blaze in the fireplace of his 1932 home, only to see smoke coming out through the walls. The fire department told him such fires were not uncommon as the fireplaces of the era were often just for show, not warmth.

Are there holes in that pipe? A typical log lighter that is used to start wood might look like what you have, but it would have holes in it. If there are no holes in the pipe, you cannot tell if there is gas coming into the line without removing the cap and putting a pressure meter on it...or lighting a match like Michael mentioned. But if you attempt the match lighting test with the cap off, you best be careful as you may end up with a flame thrower.

Below are some examples of log lighters and a gas log burner. The third one could be what you have. Often times that type of log lighter has a cap instead of being pinched on the end like the example.