This anvil is said to be about 300 lbs with no markings.  Notice the holes in the feet.  Any idea who made it?

 

Holes in the feet were added later by the owner.

Take a closeup picture of the side horn facing right, and of the front foot under the horn.  Many, many times people have said "no markings", and sometimes it is the case, but other times faint details of markings can be seen.  Also take a picture of the underside of the anvil.  

Will do.  I haven't inspected the Anvil in person.  Will do in a few days.

I'm betting it's a H-B

I'm thinking Trenton. Do you have a picture where the horn is facing?

 

Get it weighed!  Guessed weight tends to be quite far off unless the person has spent a lot of time with a large number of anvils, (in which case they should know what brand it's most likely is)  And yes the mounting holes are a retrofit by some previous owner.

It looks like a Trenton, but the holes in the feet are suspect.