Design a postcard for a gold and silver buying service dealing with estate lawyers

Information for the business: Evaluation and purchase of gold and silver bullion, coins and jewellery from estate executors, lawyers and trustees
Industry: Business
Design details: The company is The GoldSmart Network

We buy gold and silver in the form of bullion bars, coins and jewellery from estates by working with the lawyers and trustees who are acting as executor. We are a private service by appointment only at the trustee's or lawyer's offices. We are not open to the public.

We need a 5.5" by 8.5" 2 sided mailable postcard consistent with Canada Post design rules for addressed admail. On the face of the card we need the graphics and text presenting the service. On the reverse we require the company logo, return address and perhaps additional graphics or messaging if the design suits the space available.

The beneficiaries rely on our ability to correctly evaluate the precious metal items in the estate. We provide no cost evaluations. We buy if the beneficiaries wish to liquidate. There is an example of an existing postcard which contains suitable text and explains the business.
Target audience: Estate lawyers, accountants, executors and trustees dealing with the liquidation of estates that happen to contain precious metals items
Number of pages needed: 5.5" by 8.5" postcard, 2 sided
Content on the front/back side and body: See the attached example of an existing postcard we have been using for suitable copy. Logo is in the attached files. Use stock photography for a background image
Ideas for the visual style: This postcard will likely be intercepted by the receptionist at most legal and trustee firms. The card needs to look and feel like something important that should be kept in case a valued client ever has need for precious metals evaluation service as part of an estate. The piece needs gravitas, but also punch.
Things to avoid: We are not a "cash for gold" service. Pictures of money and smiling customers do not at all fit our image. We deal strictly with lawyers, accountants and trustees. We need to be memorable, but for presenting a conservative, trustworthy, discreet, professional impression.
Preferred colors: Green like the logo
Extra notes: This piece needs to exude professionalism, trust and discretion. Graphics that come to mind might include the interior of a bank vault with the big vault door and safety deposit boxes in evidence.