Duggap is correct. Here is more-specific information:
Your brass keyhole-cover is from an early "lever" version of padlock. Being marked simply "Patent," yours can date from the late-1700s through late-1800s. I think (but am not 100% certain) that the ones maked simply "Patent" are British-made. The particular shape of yours, which somewhat resembles a spear-head, is from the earlier part of that date-range. It is frequently seen on what are called "Smokehouse" padlocks. Here are a couple of photos showing a very similar brass keyhole-cover on iron-bodied "Smokehouse" padlocks. You can learn more about that variety of padlock, and see many more photos, at: Smoke House Padlocks - Antique Padlocks