Welcome to the Forum from Virginia.
I agree 100% with Lobo above. True value can only be ascertained by up close inspection with complete teardown because several components are actually serial numbered in places not viewable with just normal field stripping. For example with early Colts (like your fathers friend's) the last 4 digits of the serial number will be stamped onto the firing pin stop plate, but to view this component requires disassembly from the slide itself. Also all of these guns are ex-military and will have various government inspector initials, and proof marks, both government and Colt present on several components. Both the condition (sharpness, etc.) and appearance of these marks has a very real affect on value as the components can (and will be found) mixed, refinished, worn, replaced....or heaven forbid.....Loctited in place (grip screw bushings most common...instead of staked. Grip screws can show signs of being buggered up by the use of normal screwdrivers instead of hollow ground, etc.
None of the above is truly "bad" because GI's and unit armorers did what they had to do to keep firearms in service and in the field......but these things are of super real importance to modern day collectors (or even accumulators of MilSurp arms and history).
Another example for your Colt.....the finish can be different shades of bluing, but I really doubt Parkerizing. The magazine(s) should maybe be what was called "duo-tone" (half blued-half in the white) and the list goes on and on.
There are numerous publications that the serious collector has to judge "value" when buying or selling.
I too remember 1961 when the CMP (then DCM) would deliver a 1911 A1, direct to your front door for the princely sum of $12.62 which included shipping and handling, and tax. My remaining 1911A1 is an Ithaca (1943) all correct, and I have turned down offer of $2,500.
The Colt pictured below sold for $2,600 4 years ago, The Remington Rand went for $2,100 about 5 years ago, even the low serial number Argentine went for $1,000 with number matching mag and original grips shipped loose.
If you (and your Dad) do not want to invest in time or books, or cannot get some pictures (even cell phone pics) then I don't see a lot of valuable assistance coming from any forum, but if you are looking for just a quick value, then I would say...sight unseen, and assuming a 60% probable non- total original...then $750 to no more than $1,000 may be in order and should settle the estate and you probably won't be hurt as you are the buyer and can then take the time to truly see what you have.
On what you have stated...taking it to a LGS would be the worst...expect $200 to $250 tops.
Hope some of this helps.