These are none other than Henry Strout's creations. The only other puzzle I have from Henry is his nice Flower String Puzzle. From what I understand, Henry started doing this series of train packing puzzles for exchange since 2013 and will finish off his series in 2018. Apparently, he's got another car/tender and an engine to complete (if anyone has more accurate information or otherwise, please PM me).
These are fine works with wheels that spin, a simple coupler cum loop system to link train cars at both ends of each car and lids that are laser etched with the puzzle and IPP exchange details etc. The size of the train cars vary a bit but is pretty large and hefty with an average size of around 18cm x 10cm x 7cm. And all use just one type of wood (although I am not sure what it is).
All the puzzles bear the same style/theme...namely to pack anywhere between 8-10 irregular shaped block pieces into a train "car". Levels of difficulty also vary since each of the train cars or box contain different number of pieces and within each car, there are some protrusions or fixed restraining piece, which makes the puzzle that much harder.
Each of the train packing puzzles have been/will be either designed by Henry himself, or someone else. As I joined the Puzzle Exchange only in 2014, I missed out on the earlier first train puzzle. What I have are the train puzzles for the last three years:-
Sphinks Cargo Car
Designed by Brian Young (a.k.a Mr Puzzle Australia),
Pack 6 pieces into the box
Cutler Freight Car
Designed by Bill Cutler
Pack 10 pieces into the box
Henry's Cargo Car
Designed by Henry Strout
Pack 8 pieces into the box
In terms of difficulty, lets just say these are not so easy as they seem. In fact they are pretty challenging. The hardest I think would be the Cutler Freight Car with its 10 pieces and easiest is the Sphinks Cargo Car with only 6 pieces (I know because I was able to solve the latter) and in between Henry's Cargo Car.
A nice idea to create a series of related puzzles for exchange. And for anyone who enjoys trains and/or packing puzzles, this will be an interesting addition to your collection, that is if you can get the complete set.