I wish they would say
why they were incorrect, for each pair. Is it the button placement? The hardware to adjust them? The X rather than Y in the back? There's so little information (I'm assuming, since you didn't quote any more) that we're left to just guess. Are there no examples of correct ones offered also, for comparison?
Nevermind, found the page. It's wonderful. This is complicated, with the links and formatting and all, but read the green print below and trust me.
Everything below here is from the 2nd US Cavalry guidelines. I've added a few notes in brackets, but it's all their work, not mine.
http://www.shadowlandstudios.com/2nd_US_Cav/guidelines.html#UD
Suspenders (Braces) Were not an issued item and if worn were purchased from sutlers, sent from home, or made by the soldier. If your trousers stay up without suspenders you do not need them.
[
Here is an excellent photo of a collection of period suspenders, included as a link behind the word Suspenders above. Go by that and you can't go wrong, though of course one can't see the finer details.]
http://www.shadowlandstudios.com/2nd_US_Cav/Equipment/Shirts_and_Suspenders.jpg
Any type of
period correct civilian model is fine: all-cloth "poor boys", or adjustable (with tin, brass, or japanned steel buckles with two or three prongs that pierced the material). Separate button straps should be attached directly to the prong buckles, with the main suspender straps passing through and not sewn to them (see sample photo link). Made of canvas, drill, linen, tapestry, embroidered, crocheted, woven, or ticking. Leather ends were common.
Braces of this era were of the "X" type arrangement which crossed in the back (and were found either sewn or not sewn together in the back). Buttoned to the trousers using 4 or 6 buttons. Period photos show a large variety of choices, as well as men not wearing suspenders at all. A period correct civilian belt simply wrapped around the waist in lieu of suspenders, is a fine alternative.
Re-enactor Notes: Virtually all of the suspenders sold by event sutlers and lower-end vendors are wrong. So are most of the suspenders worn by reenactors. Clip-on suspenders are not allowed. Y - back suspenders are a post war pattern and incorrect. Flip-up clasp and sliding friction buckles are wrong. And while a type of elastic did exist during the war (and a couple sutlers such as Nick Sekela and Carter & Jasper sell braces incorporating this elastic). it sould be understood that using fully elastic suspenders would be a concession to historical accuracy.
Click here to see examples of incorrect suspenders.
[
this takes you to the image in the post above]
Quality Braces Vendors: [
The links don't work, but I'm sure a google of the name will bring you to them easily, or click on the page link above.]
Regimental Quartermaster
Carter & Jasper
Nick Sekela (#0910 elasticized, or others, see the accoutrements section)
[I have these and like them but after several years the elastic is getting stretched out, as I'm sure it did in the period.]
Note: Nick Sekela also offers period correct
elasticized braces "ends" for giving non elastic suspenders some stretch.
River Junction Trade Co. (A non-elastic suspender but with a correct pattern at a low price.)