Decent question. I'll give you a "take" on it which works for me. The following was developed to provide a jump start on understandling Brit and Continental gun values from the 1890ish to 1960ish range. Three factors are needed to "SWAG" the value of any given gun: Brand Value level of the maker's name (BV), Original Quality grade (OQ), and Current Condition level (CC)

I find nine grades of Original Quality will suffice. Note that these grades do not imply levels of durability, longevity, goodness, fineness, or any other "ity" or "ness." Rather, they imply levels of value by the current day market.

OQ1 = best work SLE (+75% engraving, high quality wood, top craftsmanship)

OQ2 = "A" Grade SLE, Greener G-125, Best SLNE, Extra finish WR Drop-Lock

OQ3 = "B" Grade SLE, Greener G-70, "A" Grade SLNE, Full engraved
WR Drop-Lock

OQ4 = "C" Grade SLE, Greener G-60, "B" Grade SLNE, WR Drop-Lock
min engraving

OQ5 = Border engraved SLE, 1/3 engraved SLNE, 1st quality BLE

OQ6 = Plain SLNE, 2nd quality BLE, 1st quality BLNE

OQ7 = Border engraving BLE, 1/3 engraved BLNE

OQ8 = Plain BLNE

OQ9 = Colonial/Farmer

Word of caution: my research indicates that certain name brands and aesthetics inject a lot of bias into perception of handling properties. Keep in mind that most high grade guns were made to order (bespoke). The bespeaker should have been able to shoot his gun at the peak of his ability. Subsequent owners are on their own for stock fit, suitability of handling factors, feel, etc.

Post photos of your guns and I'll take a swing at value.

DDA