I welcome your initiative to organize a Search-Match Round Robin (SMRR 2002)
and I had a quick look at the data.
Normally, as I'm a chemist, I always urge our XRD-users to provide chemical
information about their products, but I gave your data a first trial
without.
We use the EVA search-match software from Bruker in combination with the
PDF-2 database (release 2001).


Most probable results (numbers refer to those in the PDF-2 database):


Sample 1:       85-0335 low Quartz (these peaks were used to correct for the
2theta shift of -0.167°); 84-1997 Fluorapatite Ca5(PO4)3F.94Cl.1; 83-1764
Siderite Fe(CO3); and from residual scan 33-0863 Souzalite
(Mg,Fe)3(Al,Fe)4(PO4)4(OH)6.2H2O (or 33-0638 Goumanite, also an iron
phosphate hydroxide hydrate)


Sample 2:       don't know for sure, but must be something isostructural to
48-0475 Silicon oxide Quinuclidine Fluoride Octadecasil 20SiO2.2(C7H12NF), I
calculated for the unkown compound unit cell parameters of a = 9.0874 Ang
and c = 13.4608 Ang (tetragonal unit cell)


Sample 3:       need more information about the chemistry


Sample 4:       05-0561 Litharge PbO; 23-0333 Lead oxide sulphate
PbSO4-4PbO; 88-0552 Lead oxide sulphate hydrate (PbO)3(PbSO4)H2O; or maybe
also 73-1056 Parabutlente FeSO4(OH)(H2O)2