These plaid coats date from the late 1950's and early 1960's and were made by Pendleton. They were a yearly classic that was created in several styles and in many seasonal plaids.
It could be designed to be part of a dress set, matching a slim sheath that was worn under it. Or the plaid could be a key accent, bringing together colors from a wardrobe, so that any item worn under it had a color connection.
Matching plaids is always a problem in fit and flare or princess seamed coat styles. In looking for a current coat pattern for this simple silhouette that would lend itself to plaid, it's important to steer clear of vertical or horizontal seam lines that will need to be matched. This includes princess seam lines and other fitting seams that run from shoulder to hem. If you find a jacket with the right collar, shoulder and sleeve fit, it's possible to lengthen that down from the underarm for a full length coat. Some princess seamed coat patterns can be taped together from the hip to hem level by laying the pattern pieces together, matching the grainline, then paing them together to create a seamless coat pattern for front and back views.
In published patterns, Vogue 8841, is a lean cut coat style. It does not show buttons, so those would need to be added after checking how much overlap there is in center front. Of course, vintage patterns can be used. Keep in mind the shoulder width and armhole depth found in patterns from the mid-80's through 2000 in the least, since this coat should have a lean fit and smaller armhole than patterns from that era.