Hello. That is a nice group of Chase silks. I believe Ed Hans a board member here may have an S74-2 Chase you need.
https://t206.monkberry.com/webpics/s74cha.jpg
On Chase, I own 2 S74-1 Silks one with red ink and one with brown both TR. In the S74-2 silks I own 2 as well. One with red ink and one with blue and one OM and one TR.
As far as the Helmar silks when I started the S74Silk.com website with help from Bob C. RSST (another board member) and the data from auction houses. We came up with a total of 9 Helmar Silks known on a master spread sheet. I own one attached, its Camnitz. I also had purchased a Wolter Helmar from a dealer only to receive a Turkey Red back with an explanation he had sold the Helmar, although it was live on his site. RSST beat me to the Wolter I came to find out.
As far as SGC grading of silks I am quite critical of their grading of silks on the S74Silk website as they are inconsistent. They grade based on creasing with little regard to fraying. They will give an A to any silk that doesn't measure exactly what is outlined in the Krause Standard Catalogue. Your A graded white silks deserve a numerical grade in my opinion. If you look at the grading page on the site the comparisons are quite revealing. I have over 500 silks and they vary in size. Even though a silk is not trimmed and just slightly off size from Standard Catalogues dimensions SGC chokes on grading these. The S74-2 have several that are taller and narrow and some short and wider. SGC set criteria and are living with it even though most silk collectors are shocked by numerical grades of silks where the ad is actually frayed off.
Anyone can iron out a crease on an S74-2 but fraying is irreversible. Im not sure CSG is any better is I only own one of their graded silks (a Chase ironically). Beckett and formerly GAI seemed to be more in line with what you would expect and what is reasonable. Only if and when PSA starts to grade these will we potentially have reasonable parameters. I actually like silks because the grading really doesn't matter and doesn't effect pricing the way it does with cards.
Best of Luck