Scale: the info bar (OCR) reads "SEI 15.0kV, x5,000, WD 10.0 mm" with a scale-bar label of 1 um. The drawn scale bar is 53 px wide (columns 1202-1254), so 1 um = 53 px, i.e. about 18.9 nm per pixel (image 1280 x 1024 px, SEM area = 960 rows above the info bar, about 24 um wide).

Method: I cropped off the info bar, high-pass filtered the image, applied a Hann window and took the 2D FFT (zero-padded to 4096). The strongest peak, by a factor of about 9 over the next one, corresponds to a period of 47.6 px (sub-regions give 45.5-47.1 px). That is about 880-900 nm, central value about 890 nm.

Orientation: the wave vector lies along the image horizontal (about 2 degrees from the x axis). The structures are therefore a line/ripple (grating-like) pattern whose lines run vertically in the image (about 88 degrees from the horizontal, nearly vertical, tilted by about 2 degrees), with the periodicity measured along the horizontal direction. Weaker secondary features: a long-range modulation of about 3 um and fine texture of about 70-120 nm.

RESULT: period = 890 nm
