Both are exceptional examples, the h-block seen before, but these are much better pictures. You have had it awhile... the m-block I have not seen before and it is the more interesting of the two imo, one of the last 98k MB made. The bcd/43's show up fairly regular throughout 1943 in MB production, especially f-i blocks, but they are just a continuation of the so-called "dual codes" began earlier. The straight up ar/43 are more interesting I think... especially such a late one.
The RS scales are an interesting subject, MB used sub-contractors throughout 1942-43 for them, mostly Elite, but a few ERMA show up, along with MB made ones also (these are unmarked, only serialed), the "M" is often seen, but not always, so far in the trends about half the time and "S" and "P" are also recorded. It is not a sub-contractor marking imo, but because it is so irregular it must be some in-house marking? Some adjustment? Nearer the end the sub-contractor (Elite) scales are almost nonexistent, almost always in-house made.
For what it's worth, straight up ar/43's can be tough to find this original. The m-block is the highest "nice" ar/43 I have seen, really MB production is probably one of the more interesting of the mid-war period, damn elusive in upper grades, more so than many of the other makers. Although ar/41 and ar/42 are well known for their "scarcity" in original condition, much the same could be said of ar/43, the production ranges for all three years is very close (all three years they made roughly the same number of rifles), but what makes ar/41 and especially ar/42 so difficult is the fact so many "dual codes" (other make receivers) exist. Coupled with the fact zf41's are so common in certain blocks and the high rc-rate these years, it makes getting a really nice "straight up" mid-war MB pretty tough.
If you have the BC's or noted any sub-contractor parts not shown, I would like to hear about it... no problem if you do not have them handy, just if you know. MB trends are scanty in the later blocks of 1943, - it isn't very thorough throughout 1941-1943 either... like i said, not an easy maker to find in upper grades and often when you do, most people do not show the rifles characteristics. Probably a mix of factors involved, one MB's minimalist marking pattern, but also many are older recordings and 10 years ago or longer, most people didn't take as good pictures as today (cameras are more common and better today too, - about the only thing better today is the cameras..)