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As noted, from the 1979 catalogue.
There was a period in which we did not exactly cover ourselves in glory, during which the No. 89L had added the suede lining but had no sight rails (and no sight channel as in yours). We added the rails when a holster actually came back with a High Standard Trophy still in the holster and its front sight firmly hooked through the suede lining. The lining's glue had been loosened by the oil we apply/applied for colour, and creating a bubble of leather, the hooked sight was acting as if it had caught a big bass.
Bear in mind that everyone in the biz was trying to get their head around target sighted pistols being carried in holsters. Neale's nominal effort at Safariland notwithstanding (lots of failures of that second set of stitching that replaced the forward fold) the pistols were not designed by their makers to be holstered; so the front sights weren't ramped accordingly.