There are unfortunally various problems, firstly the Amberg was mashiner /finisher not supply of blade blanks as this was Herder in that cases, secondly You present here a refurbishment mostly from S98/05aA to S98/05nA when was applied the flashguard and crossguard ears were removed. Amberg ended finishing bayonets with 1915. The inspector proof were moved to Fichtel Sachs into period of 1916.
The period of 1914 which is confirmed was K proof on KS98 bayonets (all parts only K proofed, link to R.Wiliams book above), continued into early 1915 with K letter on S98/05aA configuration ( greek S14 and picture in my answer nr2 here and Voronov book), by middle of 1915 the inspector was changed to J stamp, which is visible on various samples with K on blade but 2xJ on pommel in links that i provided to You in my answers here above, here Your last presented piece is switch from inspector J to M (crossguard is part from previous production proofed J).
Normally by prewar production one inspector was added on all parts of bayonet, by switch of inspector or by refurbishment offcoarse the markings could be different proofs but only 2 letters normally as the pommel one is a definitive last proof not the blade proof, by 3x different proofs is most as real there was done some rework, in this case it should refurbishment with new flashguard and grips rework and reacceptance. There exist many samples in untouched condition. You could look at Solingen production in war period, there are one inspector proof on all parts as normal.
The switch to S98/05nA was done in Bavaria post september 1915, majority of K proofed Amberg should be made from period of S98/05aA and when they are with flashguards it means they were reworked directly post production to new S98/05nA standarts, which have smaller ears on crosspiece, flashguard and reworked grips.
Anyway for me is clear here the presented proof letter on first S14 bayonet is not R but K, which is confirmed on various period other bayonets as KS98, S98/05 1914 and early 1915 made or proofed in Bayern.