The FTSE 250-listed investment group said the initial consideration for the acquisition comprises £79mln in cash - funded from internal cash resources and a proposed £60mln equity placing - and the issue of 1.0mln new Rathbones shares worth £25mln.
The firm said a further contingent consideration, earn-out payments and incentivisation awards of up to 5.8mln Rathbones shares may also be payable depending upon the achievement of synergies that deliver additional earnings accretion.
Rathbone said it expected underlying earnings per share accretion of at least 8% and return on investment of approximately 13% in the third year following completion of the deal.
It added that the transaction is further expected to be marginally EPS accretive on an underlying basis in the first full year following the acquisition.
”Ideal strategic, professional and geographic fit”
Philip Howell, Rathbones CEO commented: "Speirs & Jeffrey represents an ideal strategic, professional and geographic fit with Rathbones and we look forward to working together both to develop our business in Scotland and deliver compelling returns for our shareholders.”
The group said the acquisition is subject to approval by the FCA and is expected to complete during the third quarter of 2018.
In a separate statement, Rathbone it will undertake an accelerated bookbuild placing with institutional investors of new shares representing approximately 5% of the company's existing issued ordinary share capital at a price of 2,500p per share to raise gross proceeds of approximately £60mln.
Rathbone shares closed trading on Wednesday at 2,502p each.