You know I rather think it is, good luck with it, I remember mine had superb handling, indeed she may have a bit of a shock!
The steering kingpins very much look like a Trice, I can't see the top end of the seat stays, I presume that it will look like a half tube brazed on to the stays, held on with 'Jubilee clips', under the seat might be, a bottom bracket shell with caps on to fix the rest stays to the main chassis tube., You mentioned the tyres,being not the usual 20", that would be right, they were not the standard '406' size now
If I am right, she is a bit of a rare beast indeed,not many survived, the ancestor of today's ICE Trikes now.
'Bin chance'!