Corner-Notched Strap for a Seiko 7N42-7189
A Seiko 7N42-7189 does not take a straight-cut strap. The case shoulders close in over the lug gap, so a flat 22 mm end fouls the case before the spring bar ever seats. This order from Massachusetts came in with the three numbers that solve it: A 22 mm, B 8 mm, C 5 mm.
Build sheet
| Watch | Seiko 7N42-7189 |
| Strap type | Custom corner-notched |
| A (full width) | 22 mm (0.87 in) |
| B (notch depth) | 8 mm (0.31 in) |
| C (shoulder cut) | 5 mm (0.20 in) |
| Leather | Black Epsom |
| Length | 75/125 mm (3.0 in / 4.9 in) |
Why these choices
Corner-notching is the pattern where the strap keeps its full width across the body and loses material only at the two outside corners of the end, so the strap tucks under an overhanging case. It is the same geometry a Cartier Santos needs, and it is what most integrated-look and vintage dress cases need once you actually put a caliper on them. The alternative — dropping to a narrower straight strap — leaves visible daylight at the lugs and is the single most common reason a replacement strap looks wrong on a watch like this.
The three measurements are not interchangeable. A is the full width the body runs at, B is how far back the notch is cut from the tip, and C is how much comes off each corner. Get C wrong by a millimetre and the strap either binds against the case or leaves a gap. We cut to the numbers we are given rather than to a template, which is why the order form asks for them separately — and why we recommend having a jeweler take them if you are not confident with a caliper.
Black Epsom is a good match for a build like this. It is a stamped-grain calfskin, the same leather used in Hermès bags, and it is light and scratch-resistant — useful on a strap whose corners are already carrying a cut. The stamped grain also stays uniform across the notched section, so the cut edge does not draw attention the way an open-pored veg-tan can.
★★★★★
“I got the brown crocodile strap and had it corner notched from 18mm to 16mm. I’ve fallen in love again with my 30+ year old Seiko! The strap & customization are absolutely perfect… turn around time was less than two weeks.”
Mark R. · Custom corner-notched strap
Questions we get on this build
How do I measure for a corner-notched strap for a Seiko 7N42-7189?
Measure A across the lug gap, then measure how deep the case overhangs that gap (B) and how much width is lost at each corner (C). Photographs of the bare lugs next to a ruler help us sanity-check the numbers before we cut.
Is corner-notched the same as center-notched?
No. Corner-notched (A/B/C) removes material at the two outside corners. Center-notched (X/Y/Z) removes a tab from the middle of the end. Which one you need depends on the case, not the brand — send photos if you are unsure.
Every strap is cut to order — allow 2 to 3 weeks to delivery. Start with the corner-notched builder or see the full range of notched straps.