Looks good - though to be honest on the face of it it's more similar than different to the product I linked with 80% nickel (other components not specified) and 0.004" = 0.1mm thick, vs for my one 0.15mm thick 80% nickel supposedly MuMetal.. "conforming to
ASTM A753 Alloy 4, MIL-N-14411C Composition 1, and 1J79" - whatever that means.
On closer review of their links and language for the one I got, it appears, despite their use of the term MuMetal, it's likely it's not actually official MuMetal, but some equivalent/similar composition from a different and cheaper source than the
MuMetal trademark owner Magnetic Shield Corp who're quite protective of their trademarked name. The range of linked specs are all similar to MuMetal but different names e.g. MuShield
https://www.mushield.com/material-sales/hymu-80-magnetic-shielding-alloy-astm-a753-alloy-4/
ASTM- A- 753, Alloy 4
A.K.A. Hipernom, HyMu 80, Moly Permalloy, Magnifer 7904; is a soft magnetic nickel-iron alloy with about 80 % nickel, 4.2 – 5.2 % molybdenum, a saturation induction of approximately 8,000 Gauss, the highest technically obtainable permeability,( Max >350,000) and a very low coercive force.
Not sure that helps at all - other than to say there's a lot of suppliers with very similar materials out there!
EDIT: I see the spec sheet for your one refers A753, type 4! Snap!