Anyone ever seen this type of construction?
Not for a shed, commercial applications, yes.
Looks like somebody did a nice job from what I can see Joe.
I agree with Dale. Never seen anything like it in a shed but, I don’t know why there would be anything wrong with it. It looks well done.
I can’t tell from the last two pictures thought, was the plywood roof sheeting fastened to those steel joists with nails or screws. If it’s nails, I’d be concerned that they wouldn’t hold. If it’s screws, the I’d say “cool.”
Hi. Joe;
Looks good, but my only questions would be the concern of the gauge of material; 18, 20, or 25 gauge material?
Anchorage to slab, required for Ballast.
Amount of screws not evident, example, #10 hex head tex on all stud to stud connections.
Collar ties with only one screw.
Ledgers seems to be lacking screws.
Amount of storage
The roof sheathing appears to have been screwed with #8 drywall teks, so it must have been at least a 20 gauge material.
Other than that, it looks good.
Marcel 
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somebody will commercial construction experience built it.
i cant’ tell what is holding up the ledger board that supports the “attic” floor & i agree with marcel that one screw in the collar tie is not adequate; however the floor joist should keep the system from spreading and so probably it isn’t an issue.
I can see this crying in a shed with the usual high humidity and the high day time temperatures and cool evenings.
I think the metal will drip regularly.
The collar ties are up so high, they probably aren’t doing much of anything, anyway. A rule-of-thumb for collar ties is that they should not be above the upper third of the dimension between the ceiling joists and the ridge. The roof is probably small enough that the joists will tie it adequately, as was mentioned.
Joe, unless I am very much mistaken this is really post and beam construction with metal stud curtain walls and roof system, I believe this was kit built and looks OK to me, the only thing I cannot see from the pictures is diagonal bacing of the structure to prevent racking.
Regards
Gerry
Mr. Beaumont makes a point about post and beam construction. The attic floor should act as a diaphragm to prevent racking.
I do see a 4x4 post where two ledger boards abut, but I don’t see how it is supporting the the ledger. The metal ledger below the wood one makes it appear that the the studs are intended to support the ledger, but there is only one screw per stud. It does appear that the builder was rather stingy with screws throughout. There is plywood evident at the corner of the wall that appears to provide wind bracing.
Jim king