[rhmc24]

Your muzzle shows finesse. Most have an almost square muzzle hole - maybe thats the way they get with a lot of use. As stated above, it is common for the barrel to become almost frozen on the thread due to rust.

Some thoughts about barrel removal, offered not as an instruction but a review of my experience over half a century. First I would decide whether best to leave the pistol as-is or get involved with 'heroic' methods.

Per above, it is good to apply penetrant inside and outside the barrel at the frame joint and allow it to sit over night. Heating and cooling can help due to parts expanding and contracting at different rates. First cleaning any oil, I have heated the entire gun in kitchen oven (grip removed) to close to broil temperature and quickly quench the frame in cold water. Cooling the frame quickly can shrink it away thus tending to free the seizure.

The spanner and the grip will not stand much torque without damage. To hold the barrel without damage (if you don't have a barrel vise or equivalent) I bore a hole in hardwood as near as possible to the diameter of the barrel and cut it lengthwise with the hole so as allow surrounding the barrel, apply rosin to improve traction and grip it as tightly as possible in the vise.

Grip the sides of the frame between where the barrel joins and just behind the nipple, being careful not to squeeze the part where the mechanism is located.

Attempting a cheerful note - your pistol looks good enough that it may never have been fired or fired very little and a little heat may loosen old grease and the barrel turn off easily. Best!