  Even at modest amplification, the optical depth to gravitational lensing
through the Galaxy is $<10^{-5}$. However, the large apparent
isotropic-equivalent energy of GRB 221009A coupled with a path through low
Galactic latitude suggests that the conditional probability that this
particular GRB was lensed is greater than the very low a priori expectation.
With the extreme brightness of the prompt emission, this Galactic lensing
hypothesis can be constrained by autocorrelation analysis of Fermi photons on
0.1-1000 ms timescales. In relating lensing mass, magnification, and
autocorrelation timescale, I show that a lensed-induced autocorrelation
signature by stellar lenses falls below the minimal variability timescale (MVT)
expected from a black hole central engine. However, lensing by Galactic dark
matter MACHOs ($M_l > 10-1000\,M_\odot$) could be confirmed with this approach.
Regardless, at a peak $\gamma$-ray photon rate of $>30$ ms$^{-1}$, GRB 221009A
represents a prime opportunity to measure the smallest MVTs of GRBs.
