TLG hasn't always been particularly careful about their set numbering, so the community has taken to adding -1 to the end of the set number to handle cases where there may be duplicate set numbers used by TLG. For example, here's what we refer to as 8858-1:
As others have pointed out, this also helps to track minor adjustments to sets (re-...
As jncraton pointed out some numbers have been reused by different sets, however there are other cases too.
A good example is 10242 MINI Cooper. During production of this set TLG has decided to change the box from original squarish size, which is designated as 10242-1 on Bricklink
to rectangular version of the box, so Bricklink used 10242-2 to mark this ...
Searching Bricklink.com for all sets that have Part # 30056 - Fence 4 x 4 x 2 Quarter Round Spindled with 2 Studs.
We get the image of your plane, which is from Set #3451 - Sopwith Camel.
Looks like your model needs a serious dusting.
Looks like LEGO switched up the numbering of the CUUSOO/Lego Idea sets. The Ghostbusters set is officially #006 as can be see on the Lego.com site and now that review units of the Exo-Suit have been released to several Lego related blog sites, it has the number #007 on it.
Official LEGO Shop listing of Ghostbusters set Click on the box image
Review of Exo ...
If the parts on the background are from the bags its probably:
70614-1: Lightning Jet
370223: Technic Brick 1X8 in Bright Blue. This is the only set released after 2017 with this part.
It also contains:
302126: Plate 2X3 in Black
428623: Roof Tile 1X3/25° in bright blue
The letters typically represent the initials of the set designer. See more discussion on this topic in this EuroBricks forum thread.
For example, the initials "MB" stand for Marcos Bessa, where "MS" is for Mark Stafford.
Some other sets also carry set designer initials, sometimes subtly incorporated in the build (I believe Jamie Berard, the famous Modular ...