The Lesley M. prospect is located on the northwest bank of Lesley (Cooper) Creek about 1.7 kilometres above the confluence with Cascade Creek, approximately 4.0 kilometres south of the south end of Long Lake, 15 kilometres north of Stewart.

The area is underlain by Lower Jurassic Unuk River Formation (Hazelton Group) rocks (Open File 1987-22). These rocks, striking mainly north to northeast, comprise predominantly andesitic tuffs and breccias with, in places, intercalated hematitic sediment lenses. Northwest trending porphyritic granodiorite dikes (Premier Porphyry dikes) and north trending lamprophyre dikes occur in the area (Bulletin 58).

The No. 4 (upper) and No. 3 (lower) tunnels were driven on a 0.7 to 1.2 metre wide vein which strikes 010 degrees and dips 45 degrees west (Bulletin 58, Figure 52). Few details are available on the mineralization. The vein apparently lies in a 28 metre wide shear zone that also strikes 010 degrees and dips 45 degrees west. The zone is more altered, silicified and mineralized on the hangingwall and footwall sides. Randomly oriented stringers of mainly argentite occur across widths of about 1.8 metres on the hangingwall and footwall. Stringers of massive sulphide, 2 to 5 centimetres wide, locally mark the hangingwall. The central portion of the zone, about 24 metres wide, is pyritic but contains few argentite stringers. Samples across the vein in the No. 4 tunnel assayed up to 210.9 grams per tonne silver and trace gold across 0.7 metre (Bulletin 58, Figure 52).

The No. 2 tunnel, about 205 metres west of the No. 4 tunnel, was driven on north-northeast and east-northeast trending veins. The best sample assayed 519.1 grams per tonne silver and trace gold across 0.2 metre (Bulletin 58, Figure 52).

In 1918, Bush Mines Limited held the Leslie claim group. The following year three tunnels (Nos. 2, 3 and 4) were emplaced. In 1925, National Silver Mines Ltd. took over the development of the property and carried out some drilling (9 holes totalling 888 metres?). That year, Sebakwe and District Mines acquired control of the property. Subsequently, Selukwe Gold Mining and Finance Company gained control of Sebakwe. Sebakwe carried out further drifting and crosscutting in 1928. In 1936, Sebakwe was amalgamated with Premier Gold Mining Co. Ltd. and B.C. Silver Mines Ltd. to form Silbak Premier Mines Limited. No further work has been reported on the prospect since the 1920s.