Electron-diffraction measurements have been conducted on thin freestanding liquid crystal films of n-pentyl-4’-n-pentanoyloxy-biphenyl-4-carboxylate (54COOBC). This compound undergoes the smectic-A-hexatic-B-crystal-B phase sequence, but its thin films exhibit power-law thermal anomalies at the smectic-A-hexatic-B transition which are not predicted in the theory of defect-mediated melting in two dimensions, despite the apparent absence of herringbone order. We have determined the 6n-fold bond-orientational order (BOO) parameters C-6n and positional correlation length xi in a two-layer film as a function of temperature in the hexatic-B phase. The results of C-6n are consistent with the scaling relation C-6n = C-6(sigma(n)), where sigma(n) = n(2), as expected in a two-dimensional XY system.