Can anyone think why someone has done this to an otherwise ordinary hammer?
https://www.ebay.co.uk/itm/115431866183?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D240037%26meid%3D2f3b3ac323bf42c191f540451e33c221%26pid%3D101195%26rk%3D3%26rkt%3D12%26sd%3D144619724608%26itm%3D115431866183%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv9PairwiseWebMskuAspectsV202110NoVariantSeedWithRevOpt90NoRelevanceKnnRecallV1%26brand%3DUnbranded&_trksid=p2047675.c101195.m1851&amdata=cksum%3A1154318661832f3b3ac323bf42c191f540451e33c221%7Cenc%3AAQAHAAABQAoNKsJM3HOHkM0OuV9XKcsoXSMLk3wBBxTIYdgqgcSsJbD%252BWQW2%252Fi9%252FH9y8TZ%252F9TU3Es3oTKRolT9u5mF91RnSGjcRDdDpXI3GNi9QMheFP623sd2luaveQWWobQW5%252FEbDAGMZ8H5RyOHfbCmoEhpXGwqxDWpbkAAb0PS6UCda%252BAuZrgRTgIWq3T9yeDK0Vx1ywl2cfbLD%252FunhNsViLxJLKTkYvw1ca%252FjNJewwa1QYHYl%252Fz0KaZvgtknaf9Xsq9ZNcDsPISJB%252BHZkmUrja8gcNCNFyVJ%252FqZv2Kn6KCVMwH66yca%252BXEf3Xhi6JuSUS2Pzdx%252B%252BC3VS%252FLDibeALYD0j6jqBUwf96KfgRiLOcaV5vJc%252BluIraJYZkzJdRtPTCQY6FlXJjPRnOVpyFJeX98kWyQPRtpzmStrgp5GBcQLWZU5%7Campid%3APLX_CLK%7Cclp%3A2047675