The main difference between a model 1100 and an 1187 is, the 1100 is a semi-automatic auto loading shotgun, and the 1187 is a pump shotgun.
Sorry, but that doesn't appear to be correct-the 1100 and 1187 are both autoloading shotguns-the Remington Pump guns are the 870 and the 887. The 105 is also a new autoloading gun. I still can't see any difference between the 1100 and the 11 87.....
The 11-87 "replaced" the 1100 for a short time. The main difference is the gas system which handled light loads and magnums without any adjustment. If you wanted a magnum in the 1100, it had a single gas port and did not handle light loads with that barrel. the 11-87 did a better job of that function than the 1100. However, the 1100 was so popular that Remington had to reintroduce it, especially among clay target shooters. Hope this helps.
1100 is a Remington, not Browning.
The 1100 designation for a Remington shotgun is the model number. Remington makes the 1100 model in a trap version and a field version.
with the L prefix to the serial number,this would indicate that your model 1100 Remington shotgun was made in 1991.
Visit the Remington web site.
The difference is that the Remington 1100 3 inch mag will take three inch mangnum loads and shorter where one that doesn't say 3 inch on the barrel will only take two and three quarter inch shotshells or smaller.Trying to put a three inch inch a gun that is not designed to will cause extreme stress on the barrel and will get jamed in a pump or automatic shotgun.
You can request an owner's manual for free at the Remington website.
Between 400 and 500 dollars, depending on condition of gun. 1980 brand new still in the box
At least $150 if is in good condition more if it is a 20G
100-1000 depending on specifics
150 mint condition
Best left to a gunsmith