Before 1934, gun companies did not have to put serial numbers on handguns. From 1934 to 1968 only handguns had to have serial numbers, and rifles and shotguns only had them if the manufacturer wanted to put them on voluntarily.
You might have an older Iver Johnson that was made in the early 1900s to the early 1930s that was made without any serial number. I'd take the grips off and look all over for any markings. If you want to identify this gun, register for some gun collector's website and read about old Iver Johnsons and post good clear pictures of yours, with close-ups of any writing or marks. Chances are some Iver Johnson collector will be able to tell you what you have and when it was made.
On an older revolver, you are not likely to find a model number, since they did not use model numbers. If you remove the grips, you should find the serial number stamped in the frame under the grips.
I have a 32 caliber hammerless Iver Johnson serial 45158 with a 3 inch barrel how do i find out about it
Between $5 and $50 unless it has unusual features.
That Colt .32 hammerless was made in 1924.
@1911
A Colt 380 hammerless with that serial number was made in 1915.
I found a 1903 hammerless .32 with that serial number made in 1925.
A Colt 1908 hammerless .25 with that serial number was made in 1920.
The Colt 1908 hammerless 380 with serial number 39901 was made near the end of year 1920 as the year 1921 started with serial number 40000.
The Colt 1908 hammerless .380 with that serial number was made in 1937.
1906
A Colt 1908 hammerless .25 with that serial number was made in 1916. It would be 95 years old.