When pilots call a tower - and the tower isn't too busy, they have to say _"Metro Tower, Cessna 833PB, 10 miles north with Delta inbound for (request)"_, which means they have the current weather. Each time there's a weather update that alphanumeric code gets updates. There are comments and things that purchasing and MRP dumps into POs and ItemMaster without alerting anyone to those updates. If these updates had an alpha code for the comment that get's incremented we could roll these non-revision changes up. For example, if units of measure are changed there's a comment saying they're updated. This change could affect how a part is ordered but unless someone is looking at the part in detail they could order the old quantity before it was silently changed. Rather if on the req you had to put the comment revision you last saw it would mean that you saw any silent changes. https://www.boldmethod.com/learn-to-fly/radio-procedures/how-to-call-air-traffic-control-on-your-initial-call-tower-approach/